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  • Liquid-liquid miscibility gaps in drug-water binary systems: crystal Structure and thermodynamic properties of prilocaine and the temperature-composition phase diagram of the prilocaine-water system

     Rietveld, Ivo B.; Perrin, Jean-Claude; Toscani, Siro; Del Barrio Casado, Maria; Nicolai, Beatrice; Tamarit Mur, Jose Luis; Céolin, René
    Molecular pharmaceutics
    Date of publication: 2013-04
    Journal article

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    EMLA cream, a ¿eutectic mixture of local anesthetics¿, was developed in the early 1980s by Astra Pharmaceutical Production. The mixture of anesthetics containing lidocaine, prilocaine, and water is liquid at room temperature, which is partly due to the eutectic equilibrium between prilocaine and lidocaine at 293 K, as was clear from the start. However, the full thermodynamic background for the stability of the liquid and its emulsion-like appearance has never been elucidated. In the present study of the binary system prilocaine-water, a region of liquid-liquid demixing has been observed, linked to a monotectic equilibrium at 302.4 K. It results in a prilocaine-rich liquid containing approximately 0.7 mol fraction of anesthetic. Similar behavior has been reported for the binary system lidocaine-water (Ce´olin, R.; et al. J. Pharm. Sci. 2010, 99 (6), 2756-2765). In the ternary mixture, the combination of the monotectic equilibrium and the above-mentioned eutectic equilibrium between prilocaine and lidocaine results in an anesthetic-rich liquid that remains stable below room temperature. This liquid forms an emulsion-like mixture in the presence of an aqueous solution saturated with anesthetics. Physical properties and the crystal structure of prilocaine are also reported.

    EMLA cream, a “eutectic mixture of local anesthetics”, was developed in the early 1980s by Astra Pharmaceutical Production. The mixture of anesthetics containing lidocaine, prilocaine, and water is liquid at room temperature, which is partly due to the eutectic equilibrium between prilocaine and lidocaine at 293 K, as was clear from the start. However, the full thermodynamic background for the stability of the liquid and its emulsion-like appearance has never been elucidated. In the present study of the binary system prilocaine−water, a region of liquid−liquid demixing has been observed, linked to a monotectic equilibrium at 302.4 K. It results in a prilocaine-rich liquid containing approximately 0.7 mol fraction of anesthetic. Similar behavior has been reported for the binary system lidocaine−water (Céolin, R.; et al. J. Pharm. Sci. 2010, 99 (6), 2756−2765). In the ternary mixture, the combination of the monotectic equilibrium and the above-mentioned eutectic equilibrium between prilocaine and lidocaine results in an anesthetic-rich liquid that remains stable below room temperature. This liquid forms an emulsion-like mixture in the presence of an aqueous solution saturated with anesthetics. Physical properties and the crystal structure of prilocaine are also reported.

  • Conformational polymorphism: The missing phase of 1,1,2,2-tetrachloroethane (Cl2HC-CHCl2)

     Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Mondieig, Denise; Zuriaga, Jose Mariano; Perez, Silvina C.; Negrier, Philippe
    Crystal growth and design
    Date of publication: 2013-05
    Journal article

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    Halogenoethane derivatives are known to exhibit different polymorphs involving a different translational, orientational, and conformational order. The 1,1,2,2-tetrachloroethane (Cl2HC-CHCl2) exhibits a normal pressure orthorhombic phase beta (space group P2(1)2(1)2(1) with Z = 8 and Z' = 2), formed by molecules with one of the two gauche conformations. At high pressure, the stable polymorph is known to be monoclinic (space group P2(1)/c, with Z = 2 and Z' = 0.5), phase alpha, in which only the trans conformer appears. In this work, we demonstrate the existence of a normal pressure metastable polymorph, phase gamma, for which the two gauche conformers show up in the asymmetric unit of a monoclinic (space group P2(1)/c with Z = 8 and Z' = 2) structure. The new phase gamma is obtained by recrystallization upon heating the glass obtained after quench of the melt. It displays shorter type II Cl center dot center dot center dot Cl contacts than the high-pressure phase alpha due to attractive and directional interactions.

    Halogenoethane derivatives are known to exhibit different polymorphs involving a different translational, orientational, and conformational order. The 1,1,2,2- tetrachloroethane (Cl2HC−CHCl2) exhibits a normal pressure orthorhombic phase β (space group P212121 with Z = 8 and Z′ = 2), formed by molecules with one of the two gauche conformations. At high pressure, the stable polymorph is known to be monoclinic (space group P21/c, with Z = 2 and Z′ = 0.5), phase α, in which only the trans conformer appears. In this work, we demonstrate the existence of a normal pressure metastable polymorph, phase γ, for which the two gauche conformers show up in the asymmetric unit of a monoclinic (space group P21/c with Z = 8 and Z′ = 2) structure. The new phase γ is obtained by recrystallization upon heating the glass obtained after quench of the melt. It displays shorter type II Cl···Cl contacts than the high-pressure phase α due to attractive and directional interactions.

  • Solid-state properties and dehydration behavior of the active pharmaceutical ingredient potassium guaiacol-4-sulfonate

     Mahé, Nathalie; Nicolai, Beatrice; Del Barrio Casado, Maria; Perrin, Marc Antoine; Do, Bernard; Tamarit Mur, Jose Luis; Céolin, René; Rietveld, Ivo B.
    Crystal growth and design
    Date of publication: 2013-05-20
    Journal article

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    Potassium guaiacolsulfonate is an active pharmaceutical ingredient that has been in use for more than a century, and it is still widely used in cough syrups. Nonetheless, no crystal structure has ever been determined to facilitate quality control. This is all the more surprising because two isomers are known to exist. A commercial sample has been studied by X-ray diffraction and thermogravimetric methods. It consists of potassium guaiacol-4-sulfonate, and it crystallizes in the monoclinic space group C2/c as a hemihydrate. The crystals exhibit uniaxial negative thermal expansion, and the electrostatic forces between the ions appear to be the major driving force of the observed displacements. Dehydration of the hemihydrate was observed above 380 K. The anhydrate has a structure similar to the hemihydrate with almost the same unit cell parameters. The dehydration kinetics points to a displacive mechanism; water molecules are located in channels, through which they leave the crystal. The structural readjustments that occur to accommodate the loss of water are driven by electrostatic interactions between the ions similar to the displacements observed for thermal expansion. Under ambient conditions (and humidity), the anhydrate is not stable and transforms into the hemihydrate.

  • Tricritical behavior of the nematic to smectic-A phase transition in the binary mixture of liquid crystal

     Mukherjee, Prabir K.; Tamarit Mur, Jose Luis
    Journal of chemical physics
    Date of publication: 2013-03-14
    Journal article

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    We propose a phenomenological model to describe the tricritical behavior of the nematic to smectic-A (N-SmA) phase transition in liquid crystal mixture. To describe the mesophase transitions in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that a tricritical point on the N-SmA phase transition line can be achieved under certain conditions. The predictive capability of the present model for determining the tricritical point of a binary mixture displaying the N-SmA transition has been demonstrated by testing with reported phase diagrams sharing both phases

    We propose a phenomenological model to describe the tricritical behavior of the nematic to smectic- A (N-SmA) phase transition in liquid crystal mixture. To describe the mesophase transitions in binary mixture, nematic and smectic order parameters have been coupled with the concentration. We show that a tricritical point on the N-SmA phase transition line can be achieved under certain conditions. The predictive capability of the present model for determining the tricritical point of a binary mixture displaying the N-SmA transition has been demonstrated by testing with reported phase diagrams sharing both phases

  • Polymorphism in halogen-ethane derivatives: CCl3-CCl3 and ClF2C-CF2Cl

     Negrier, Philippe; Tamarit Mur, Jose Luis; Del Barrio Casado, Maria; Mondieig, Denise
    Crystal growth and design
    Date of publication: 2013-02-06
    Journal article

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    The polymorphism of hexachloroethane, Cl3C−CCl3, has been reinvestigated by means of X-ray and neutron scattering. The long time unknown structure of the intermediate phase II of Cl3C−CCl3 has been determined as monoclinic C2/m, with lattice parameters a = 17.9835(21) Å, b = 10.3642(11) Å, c = 6.3014(8) Å, and β = 94.410(5)° at 323 K, Z = 6. The polymorphism of 1,2-dichloro-1,1,2,2-tetrafluoro-ethane, ClF2C−CF2Cl, has also been investigated, and the structure of the intermediate phase II has been found to be orthorhombic (Cmca, Z = 4) with lattice parameters a = 6.305(4) Å, b = 10.177(12) Å, c = 8.714 (7) Å. The high-temperature phase I of ClF2C− CF2Cl has been found to be isomorphous with the orientationally disordered phase I of Cl3C−CCl3 (body centered cubic, Im3̅m), a consequence of the pseudospherical molecular shape of halogeno-ethane C2X6−nYn (X = Cl, Y = F) molecular crystals. The similarities of the intricate disorder of the intermediate phases II of both Cl3C−CCl3 and ClF2C−CF2Cl compounds are analyzed, together with the influence of the conformational disorder appearing in the last compound.

  • Rimonabant dimorphism and its pressure¿temperature phasegiagram: A delicate case of overall monotropic behavior

     Perrin, Marc-Antoine; Bauer, Michel; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Céolin, René; Rietveld, Ivo B.
    Journal of pharmaceutical sciences
    Date of publication: 2013-05-20
    Journal article

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    Crystalline polymorphism occurs frequently in the solid state of active pharmaceutical ingredients, and this is problematic for the development of a suitable dose form. Rimonabant, an active pharmaceutical ingredient developed by Sanofi and discontinued because of side effects, exhibits dimorphism; both solid forms have nearly the same melting temperatures, melting enthalpies, and specific volumes. Although the problem may well be academic from an industrial point of view, the present case demonstrates the usefulness of constructing pressure¿temperature phase diagrams by direct measurement as well as by topological approach. The system is overall monotropic and form II is the more stable solid form. Interestingly, the more stable form does not possess any hydrogen bonds, whereas the less stable one does.

  • Comparison of the atomic level structure of the plastic crystalline and liquid phases of CBr2Cl2: Neutron diffraction and reverse Monte Carlo modelling

     Pothoczki, Szilvia; Temleitner, László; Pardo Soto, Luis Carlos; Cuello, Gabriel Julio; Rovira Esteva, Muriel; Tamarit Mur, Jose Luis
    Journal of physics: condensed matter
    Date of publication: 2013-10-18
    Journal article

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    Neutron diffraction results obtained for plastic crystalline dichlorodibromomethane (CBr2Cl2) have been modelled by means of the reverse Monte Carlo method. Comparison with its liquid phase is provided at several levels of the atomic structure (total scattering structure factors, partial radial distribution functions, orientational and dipole-dipole correlations). The results reveal that the relative orientation of neighbouring molecules largely depends on the steric effect. The small dipole moment does not have as strong an influence as the steric effect on the short-range order. Our observations fit well with earlier findings presented for the series CBr nCl4-n (n = 0, 1, 2, 4). © 2013 IOP Publishing Ltd.

  • Benzocaine polymorphism: Pressure-temperature phase diagram involving forms II and III

     Gana, Inès; Del Barrio Casado, Maria; Do, Bernard; Tamarit Mur, Jose Luis; Céolin, René; Rietveld, Ivo B.
    International journal of pharmaceutics
    Date of publication: 2013-11-18
    Journal article

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    Understanding the phase behavior of an active pharmaceutical ingredient in a drug formulation is required to avoid the occurrence of sudden phase changes resulting in decrease of bioavailability in a marketed product. Benzocaine is known to possess three crystalline polymorphs, but their stability hierarchy has so far not been determined. A topological method and direct calorimetric measurements under pressure have been used to construct the topological pressure-temperature diagram of the phase relationships between the solid phases II and III, the liquid, and the vapor phase. In the process, the transition temperature between solid phases III and II and its enthalpy change have been determined. Solid phase II, which has the highest melting point, is the more stable phase under ambient conditions in this phase diagram. Surprisingly, solid phase I has not been observed during the study, even though the scarce literature data on its thermal behavior appear to indicate that it might be the most stable one of the three solid phases. © 2013 Elsevier B.V. All rights reserved.

  • Dynamic heterogeneity in the glass-like monoclinic phases of some halogen methane compounds

     Zuriaga, M. J.; Pérez, S. C.; Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis
    American institute of physics inc. , Conf. AIP. Proc. (15517616, 0094243X)
    Date of publication: 2013-02-25
    Journal article

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    In this work we study the heterogeneity of the dynamics on the low-temperature monoclinic phases of the simple molecular glassy systems , n = 0, 1, 2. In these systems the disorder comes exclusively from reorientational jumps mainly around the C3 molecular axes. The different time scales are determined by means of the analysis of the spin-lattice relaxation time obtained through Nuclear Quadrupole Resonance (NQR) technique. Results are compared with those obtained from dielectric spectroscopy, from which two a- and ß-relaxation times appear. NQR results enable us to ascribe with no doubt that the existence of two relaxations is due to dynamical heterogeneities which are the consequence of the different molecular surroundings of the molecules in the asymmetric unit cell of systems here studied. © 2013 American Institute of Physics Published online 25 febrero 2013

  • Crystal structure and solid-state properties of 3,4-diaminopyridine dihydrogen phosphate and their comparison with other diaminopyridine salts

     Mahe, Nathalie; Nicolaï, Béatrice; Allouchi, Hassan; Del Barrio Casado, Maria; Do, Bernard; Céolin, René; Tamarit Mur, Jose Luis; Rietveld, Ivo B.
    Crystal growth and design
    Date of publication: 2013-02
    Journal article

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    3,4-Diaminopyridine is an active pharmaceutical ingredient for the treatment of Lambert-Eaton myasthenic syndrome (LEMS). It is 3,4-diaminopyridine dihydrogen phosphate that has become the active ingredient of choice. As part of a larger study for the development of this drug, solid-state studies have been carried out. At room temperature, the crystals are monoclinic (C2/c). Dihydrogen phosphate anions H2PO4 - form infinite chains parallel to the b axis, and these chains can be considered as macroanions (H2PO4)8. The organic cations form hydrogen bonds with the macroanions bridging them together. A negative thermal expansion is observed along the [103] direction in the crystal, which coincides with the direction of chains of interchanging anions and cations. The crystal packing shows similarities with the hydrogen tartrate salt as illustrated by a Hirshfeld surface analysis. This phosphate and this tartrate salt are also the two diaminopyridine salts that have been selected for therapeutic use because of their appropriate physical properties. © 2012 American Chemical Society.

    3,4-Diaminopyridine is an active pharmaceutical ingredient for the treatment of Lambert−Eaton myasthenic syndrome (LEMS). It is 3,4-diaminopyridine dihydrogen phosphate that has become the active ingredient of choice. As part of a larger study for the development of this drug, solid-state studies have been carried out. At room temperature, the crystals are monoclinic (C2/c). Dihydrogen phosphate anions H2PO4 − form infinite chains parallel to the b axis, and these chains can be considered as macroanions (H2PO4)∞. The organic cations form hydrogen bonds with the macroanions bridging them together. A negative thermal expansion is observed along the [103] direction in the crystal, which coincides with the direction of chains of interchanging anions and cations. The crystal packing shows similarities with the hydrogen tartrate salt as illustrated by a Hirshfeld surface analysis. This phosphate and this tartrate salt are also the two diaminopyridine salts that have been selected for therapeutic use because of their appropriate physical properties.

  • Dynamic heterogeneity in the glass-like monoclinic phases of some halogen methane compounds

     Zuriaga, M. J.; PÉREZ, S.C.; Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis
    Slow Dynamics in Complex Systems
    Presentation's date: 2012-12-03
    Presentation of work at congresses

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  • Polymorphism in halogen-ethane derivatives: CCl3-CF2Cl and CF3-CF2Cl

     Negrier, Philippe; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Pardo Soto, Luis Carlos; Mondieig, Denise
    Crystal growth and design
    Date of publication: 2012-01-03
    Journal article

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    Molecular crystals of halogen–ethane derivatives C2X6–nYn (X = Cl, Y = F) are known to display order–disorder phase transitions involving changes of the translational, orientational, and conformational order. The appearance of a high-temperature orientationally disordered phase with a high symmetry lattice is expected for this set of compounds in view of their “pseudospherical” molecular geometry. In this work, we present a study of polymorphism of the compounds 1,1,1,2-tetrachloro-2,2-difluoroethane (CCl3–CF2Cl) and 1-chloro-1,1,2,2,2-pentafluoroethane (CF3–CF2Cl), in which conformational disorder is not present, by combining neutron (D2B and D1B instruments at the Laue-Langevin Institute) and X-ray scattering experiments. We show that despite the close molecular shapes and molecular structures of both compounds, strong differences concerning the disorder appear in the low-temperature phase. The low-temperature phase for CF3–CF2Cl is found to be fully ordered, with a monoclinic P21/n structure (Z = 4), while that of CCl3–CF2Cl is found to be orthorhombic Pmna (Z = 4) with a disorder concerning one Cl and one F sites, each one with a fractional occupancy of 50%. Details related to the high-temperature orientationally disordered phases (both body-centered-cubic) are also given.

  • Barocaloric effect in the magnetocaloric prototype Gd 5Si 2Ge 2

     Yuce, Suheyla; Del Barrio Casado, Maria; Emre, Baris; Stern Taulats, Enric; Planes, Antoni; Tamarit Mur, Jose Luis; Mudryk, Yaroslav; Gschneidner, Karl A.; Pecharsky, Vitalij K.; Mañosa, Lluís
    Applied physics letters
    Date of publication: 2012-08-13
    Journal article

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  • Dynamic heterogeneity in the glass-like monoclinic phases of CBr nCl 4-n, n 0,1,2

     Zuriaga, M.; Perez, Silvina C.; Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis
    Journal of chemical physics
    Date of publication: 2012-08-07
    Journal article

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  • Role of steric and electrostatic effects in the short-range order of quasitetrahedral molecular liquids

     Pothoczki, Sz.; Ottochian, A.; Rovira Esteva, Muriel; Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis; Cuello, G.J.
    Physical review B: condensed matter and materials physics
    Date of publication: 2012-01-01
    Journal article

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    The study of how both steric and electrostatic interactions affect the structure of liquids formed by quasitetrahedral molecules has been undertaken in this work. We have studied trichlorobromomethane (CBrCl3) and dibromodichloromethane (CBr2Cl2), both displaying a dipole along their C3v and C2v molecular symmetry axes, respectively. The short-range order of the liquid state has been determined using neutron diffraction experiments that were modeled through the reverse Monte Carlo (RMC) technique. To study changes in steric effects due to the distortion of the tetrahedral symmetry, we have compared our results with a previous RMC modeling of carbon tetrachloride (CCl4). The subtle effects of the dipole in the structure of the liquid have been determined using a set of molecular dynamics simulations with and without atomic partial charges, being the force field validated via comparison with the diffraction data. In a first approximation, neither steric nor electrostatic interactions are able to modify the molecular ordering of a fully tetrahedral liquid such as CCl4. A more detailed analysis indicates that, although the interaction between dipoles does not have appreciable effects when aligned along the C3v molecular axes, as for the CBrCl3, it enhances the antiparallel orientation of dipoles when it is oriented along the C2v axes, as in the case of CBr2Cl2.

  • Uniaxial negative thermal expansion in crystals of tienoxolol

     Nicolaï, Beatrice; Rietveld, Ivo B.; Del Barrio Casado, Maria; Mahé, Nathalie; Tamarit Mur, Jose Luis; Céolin, René; Guéchot, Christophe; Teulon, Jean-Marie
    Structural chemistry
    Date of publication: 2012-06-17
    Journal article

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    The thermal expansion of tienoxolol has been investigated by X-ray powder diffraction up to its melting temperature. The data indicate that the expansion is anisotropic and even negative in one direction of the unit cell. The supramolecular structure formed by hydrogenbonds reflects that of a trellis, which explains the observed behavior of tienoxolol crystals.

  • Dinámica en sólidos desordenados

     Romanini, Michela; Macovez, Roberto; Ruiz Martin, Maria Dolores; Levit Valenzuela, Rafael; Pardo Soto, Luis Carlos; Del Barrio Casado, Maria; Vispa, Alessandro; Tamarit Mur, Jose Luis
    Participation in a competitive project

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  • Pressure¿temperature state diagram for the phase relationships between benfluorex hydrochloride forms I and II: A case of enantiotropic behavior

     Del Barrio Casado, Maria; Maccaroni, Elisabetta; Rietveld, Ivo B.; Macpezzi, Luciana; Masciocchi, Norberto; Céolin, René; Tamarit Mur, Jose Luis
    Journal of pharmaceutical sciences
    Date of publication: 2012-03
    Journal article

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    The active pharmaceutical ingredient racemic benfluorex hydrochloride (benfluorex–HCl) has an interesting phase behavior due to an elusive solid–solid phase transition. The stability hierarchy between different phases is often determined based on heat-related experiments only or slurry interconversion. It is shown that if pressure and volume are taken into account, not only the phase equilibria are correctly positioned in the pressure–temperature phase diagram, but the experimental data also improves. Thus, it has been found that the racemic benfluorex–HCl is enantiotropic under “ordinary conditions” with polymorph II and polymorph I, respectively, being the low- and the high-temperature phases. Above ∼151 MPa, the system becomes monotropic and polymorph II is the single stable phase.

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    Emergence of glassy-like dynamics in an orientationally ordered phase  Open access

     Romanini, Michela; Negrier, Philippe; Tamarit Mur, Jose Luis; Capaccioli, Simone; Del Barrio Casado, Maria; Pardo Soto, Luis Carlos; Mondieig, Denise
    Physical review B: condensed matter and materials physics
    Date of publication: 2012-04-04
    Journal article

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    The dynamics of a simple rigid pseudoglobular molecule (2-adamantanone) has been studied by means of dielectric spectroscopy and examined under the constraints imposed by the space group of the crystal structure determined by x-ray powder diffraction. The low-temperature monoclinic structure of 2-adamantanone, with one molecule per asymmetric unit (Z'= 1), displays a statistical intrinsic disorder, concerning the site occupancy of the oxygen atom along three different sites. Such a physically identifiable disorder gives rise to large-angle molecular rotations which inherently lead to time-average fluctuations of the molecular dipole, thus contributing to the dielectric susceptibility. The dielectric spectra for the low-temperature “ordered” phase displays a universal feature of glassy-like materials, i.e., coexistence of α- and β-relaxation processes. The former is clearly identified with the strongly restricted reorientational motions within the long-range “ordered” crystalline lattice. The latter, never observed before in fully translationally and highly orientationally ordered phases, displays all the properties of an original Johari-Goldstein β-relaxation, in spite of the strong character of this glass-like phase. These findings can be explained according to the coupling model, applied to such “ordered” phases.

  • Crystal structure and solid-state studies of aged samples of tienoxolol, an API designed against hypertension

     Mahé, Nathalie; Do, Bernard; Nicolaï, Béatrice; Rietveld, Ivo B.; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Céolin, René; Ghéchot, Christophe; Teulon, Jean-Marie
    International journal of pharmaceutics
    Date of publication: 2012
    Journal article

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    Aging of drug molecules is generally studied following regulatory procedures, i.e. under forced conditions and for relatively limited storage time; therefore naturally aged samples are rare and provide scientific reference data beyond regulatory considerations. Tienoxolol was studied after 25 years of storage in the dark under ambient conditions. About 86% of the samples still consisted of tienoxolol and the main impurity (13%) was caused by the hydrolysis of the ester moiety. Protection from humidity is therefore important. Other sensitive groups containing nitrogen and sulfur appear to be quite stable with less than 0.8% conversion over 25 years. In addition, the crystal structure has been solved. Tienoxolol orange needles were found to crystallize in the orthorhombic non-centrosymmetric space group Iba2, indicating that the crystal is a racemic compound. The unit cell parameters at room temperature are a = 10.069(5)A˚ , b = 45.831(10)A˚ , and c = 9.822(5) ˚A and the unit cell volume is 4533(3) ˚A3 with Z = 8. © 2011 Elsevier B.V.

  • Differences in first neighbor orientation behind the anomalies in the low and high density trans-1,2-dichlorothene liquid

     Rovira Esteva, Muriel; Murugan, N.A.; Pardo Soto, Luis Carlos; Busch, Sebastian; Tamarit Mur, Jose Luis; Cuello, G. J.; Bermejo, F.J.
    Journal of chemical physics
    Date of publication: 2012-03-28
    Journal article

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  • Overall stability for the ibuprofen racemate: experimental and topological results leading to the pressure-temperature phase relationships between its racemate and conglomerate

     Rietveld, Ivo B.; Del Barrio Casado, Maria; Do, Bernard; Tamarit Mur, Jose Luis; Céolin, René
    Journal of physical chemistry B
    Date of publication: 2012-05-10
    Journal article

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    Enantiomer resolution is much sought after for pharmaceutical applications, because many optically active drug molecules have only one pharmaceutically active enantiomer. Although it is always possible to force separation, it will come at a cost. The present method, based on thermodynamics, provides a relatively easy approach to investigate whether separation can be thermodynamically spontaneous. A topological phase diagram of the binary enantiomer system at 0.5 mol-fraction is constructed as a function of temperature and pressure after analysis of pressure and heat related quantities. It is demonstrated that for ibuprofen, an optically active analgesic, the racemate is the only stable solid form; the phase relationship between the racemate and the conglomerate is analogous to dimorphism with overall monotropy in pure chemical compounds.

  • Effects of internal molecular degrees of freedom on the thermal conductivity of some glasses and disordered crystals

     Krivchikov, A.I.; Korolyuk, O.A.; Sharapova, I.V.; Tamarit Mur, Jose Luis; Bermejo, F.J.; Pardo Soto, Luis Carlos; Rovira Esteva, Muriel; Ruiz Martin, Maria Dolores; Jezowski, A.; Baran, J.; Davydova, N. A.
    Physical review B: condensed matter and materials physics
    Date of publication: 2012-01-30
    Journal article

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    The thermal conductivity κ(T ) of the fully ordered stable phase II, the metastable phase III, the orientationally disordered (plastic) phase I, as well as the nonergodic orientational glass (OG) phase, of the glass former cyclohexanol (C6H11OH) has been measured under equilibrium vapor pressure within the 2–200 K temperature range. The main emphasis is here focused on the influence of the conformational disorder upon the thermal properties of this material. Comparison of results with those regarding cyanoclyclohexane (C6H11CN), a chemically related compound, serves to quantify the role played by the terminal groups -OH and -CN on the phonon scattering processes. The picture that emerges shows that motions of such groups do play a minor role as scattering centers, both within the low-temperature orientationally ordered phases as well as in the OG states. The results are analyzed within the Debye-Peierls relaxation time model for isotropic solids comprising mechanisms for long-wave phonon scattering within the OG and orientational ordered low-temperature phases, as well as others arising from localized short-wavelength vibrational modes as pictured by the Cahill-Pohl model. By means of complementary neutron and Raman scattering we show that in the OG state the energy landscapes for both compounds are very similar.

  • FABADA: a fitting algorithm for bayesian analysis of data

     Pardo Soto, Luis Carlos; Rovira Esteva, Muriel; Busch, S.; Ruiz Martin, Maria Dolores; Tamarit Mur, Jose Luis
    Journal of physics: conference series
    Date of publication: 2011-10-14
    Journal article

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  • Topological and experimental approach to the pressure-temperature-composition phase diagram of the binary enantiomer system d- and I-camphor

     Rietveld, Ivo B.; Del Barrio Casado, Maria; Espeau, Philippe; Tamarit Mur, Jose Luis; Céolin, René
    Journal of physical chemistry B
    Date of publication: 2011-01-31
    Journal article

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    In 1981, Jacques, Collet, and Wilen already put forward the idea to use pressure to influence equilibria in binary enantiomer systems in analogy with temperature (Jacques et al. Enantiomers, Racemates and Resolutions; John Wiley & Sons: New York, 1981). Whereas temperature is used routinely to study phase equilibria, pressure is an all but forgotten parameter. This is therefore possibly the first paper on the influence of pressure on a binary enantiomer system: d- and l-camphor. The study consists of two parts, a topological approach, which uses data obtained from routine measurements (differential scanning calorimetry, X-ray diffraction), and the experimental determination of phase transitions as a function of pressure and temperature. This has resulted in two topological pressure-temperature phase diagrams of the pure enantiomer d-camphor and of the racemic mixture dl-camphor; both have been verified by the experiments as a function of pressure. In turn, these results have been used to construct part of the pressure-temperature-composition phase diagram of d- and l-camphor. A method to obtain the excess Gibbs energy from these binary phase diagrams as a function of pressure is proposed

  • From figh-temperature orientationally disordered mixed crystals to low-temperature complex formation in the two-component system (CH3)3CBr + Cl3CBr

     Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Mondieig, Denise; Negrier, Philippe
    Journal of physical chemistry B
    Date of publication: 2011-02-02
    Journal article

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    The phase diagram of the two-component systems (CH(3))(3)CBr + Cl(3)CBr has been experimentally determined by means of differential scanning calorimetry and X-ray powder diffraction techniques from the low-temperature ordered phases to the liquid state. Before melting, both components have the same orientationally disordered (OD) face-centered cubic (FCC) and rhombohedral (R) phases, and the two-phase equilibria [FCC + L] and [R + FCC] are accounted for by means of the existence of an isomorphic relationship between the OD phases of pure compounds. The thermodynamic assessment of such equilibria enables us to get the excess properties of the involved OD phases and to rationalize the existence of a maximum and a minimum in the [R + FCC] equilibrium on the basis of the contribution of the entropic term in the excess Gibbs energy function. At low temperature, two complexes, (CH(3))(3)CBr:Cl(3)CBr (1:1) and (CH(3))(3)CBr:2Cl(3)CBr (1:2), appear. The structures of 1:1 and 1:2 complexes have been determined to be monoclinic (P2(1)/n, c, Z = 4) and hexagonal (P6(3), Z = 6). Within both "ordered" structures, the Cl(3)CBr entities of the asymmetric unit were found to be disordered so that sites have fractional occupancies of 0.75 and 0.25 for Cl and Br atoms, in the same way that it occurs for the low-temperature monoclinic (C2/c, Z = 32) phase of Cl(3)CBr. Finally, the existence of complexes is connected with the special intermolecular interactions appearing between a methyl group and a halogen, as previously inferred by Calvet et al. [T. Calvet et al. J. Chem. Phys.1999, 110, 4841].

  • Inverse barocaloric effect in the giant magnetocaloric La-Fe-Si-Co compound

     Mañosa, Lluís; González-Alonso, David; Planes, Antoni; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Titov, Ivan S.; Acet, Mehmet; Bhattacharyya, Amitava; Majumdar, Subham
    Nature communications
    Date of publication: 2011-12-20
    Journal article

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  • Tyrosine alkyl esters as produg: the estructure and intermolecular interactions of L-tyrosine methyl ester compared to L-tyrosine and its ethyl and n-butyl esters

     Nicolaï, Beatrice; Mahé, Nathalie; Céolin, René; Rietveld, Ivo B.; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis
    Structural chemistry
    Date of publication: 2011-01-25
    Journal article

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  • Prevalence for the universal distribution of relaxation times near the glass transitions in experimental model systems: Rodlike liquid crystals and orientationally disordered crystals

     Martínez García, Julio Cesar; Tamarit Mur, Jose Luis; Rzoska, S.J.
    Journal of chemical physics
    Date of publication: 2011-04-13
    Journal article

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    Recently, Nielsen et al. [J. Chem. Phys. 130, 154508 (2009); Philos. Mag. 88, 4101 (2008)] demonstrated a universal pattern for the high frequency wing of the loss curve for primary relaxation time on approaching the glass transition for organic liquids. In this contribution it is presented that a similar universality occurs for glass-forming liquid crystals and orientationally disordered crystals (plastic crystals). Empirical correlations of the found behavior are also briefly discussed

  • Solid-State Studies of the Triclinic (Z¿ = 2) Antiprotozoal Drug Ternidazole

     Mahé, N.; Perrin, M.A.; Del Barrio Casado, Maria; Nicolai, B.; Rietveld, I.B.; Tamarit Mur, Jose Luis; Céolin, R.
    Journal of pharmaceutical sciences
    Date of publication: 2011-05-01
    Journal article

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  • Dynamics in Orientationally Disordered Solids  Open access  awarded activity

     Martinez Garcia, Julio Cesar
    Defense's date: 2011-07-15
    Department of Physics and Nuclear Engineering, Universitat Politècnica de Catalunya
    Theses

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    The key features of dynamics of ultraslowing glass forming systems are their universality in diversity. Its origin is recognized as one of the greatest challenges of condensed matter physics and materials engineering in the XXI century. Similar phenomena are observed on approaching the glass transition in low molecular weight supercooled liquids, polymers, colloidal fluids as well as in solids, for instance in orientationally disordered crystals, spin glass-like magnetic, vortex glasses. Pre-vitreous dynamics is also proposed as a general reference for the category of complex liquids/soft matter systems. The upsurge of the primary relaxation time or related dynamical properties is the basic physical phenomena of the still mysterious previtreous behavior. This means a much more pronounced slowing down than the Arrhenius pattern observed far above the glass transition temperature. Portraying this behavior constitutes one of key checkpoints for theoretical models developed to unwind the glass transition puzzle. However, none of the aforementioned features can answer the understanding that governs the increase of relaxation time in liquids upon cooling. In this thesis we focus on the above questions studying the dynamics of some materials for which their molecules can retain a translational order being orientationally disordered between them upon cooling, which are referred to plastic phases or orientationally disordered (OD) crystalline phases. The work presented in this thesis potentially extends the knowledge of dynamics of OD phases and orientationally glasses (OG), a research topic which has gained interest during the last decades. Through this study, especial attention has been devoted to the phenomenological equations accounting to the temperature dependence of the mean relaxation time describing the orientational dynamics .The study was carried out by the use of BDS as well as two complementary experimental techniques. We show distortion-sensitive and derivative-based empirical analysis of the validity of leading equations for portraying the previtreous evolution of primary relaxation time. A new method for studying the dynamics of glass forming systems is introduced and the minimization procedure is validated and discussed. We present the results divided in two topics, the dynamics of the pure compounds and mixed crystals and the derivative analysis through different existing models. In the first topic we focus on the dynamics of the pure compounds and mixed crystals formed between cycloheptanol and cyclooctanol as well as the a-relaxation dynamics of 1-cyano-adamantane and its mixtures with 1-chloro-adamantane. The second topic is divided in two groups of models, linearized and non-linearized models. In the linearized models we show the application of the derivative based, distortion-sensitive analysis to liquid crystals (LC) and OD phases. We also discuss the results concerning to the cases of the olygomeric liquid epoxy resin (EPON828), neopentylalcohol and neopentylglycol mixture, isooctylcyanobiphenyl and propylene carbonate. The possible empirical correlations between one of the linearized models with the universal pattern for the high frequency wing of the loss curve for primary relaxation time for LCs and OD phases is also shown. In the final part we show that the form of the equation recently introduced by Mauro et al. does not allow a similar straightforward linearization procedure. Unlike the previous models, the involved parameters are not correlated with the slope and the intercept of a linear function. In order to solve this problem, we have introduced the concept of the enthalpy space. The evidences of the existence of crossovers as well as quantitative descriptions are discussed. We show also a new procedure for detecting the crossover in a very easy way. A new kind of crossovers which seems to be impossible to be detected by the classical Stickel transformation is presented.

    La principal característica de la dinámica de sistemas vítreos viscosos, es su universalidad en la diversidad. Su origen es uno de los mayores desafíos de la física de la materia condensada y de la ingeniería de materiales en el siglo XXI. La fenomenología típica de las fases vítreas se observan cerca de la transición vítrea en líquidos subenfriados de bajo peso molecular, polímeros, fluidos coloidales, así como en los sólidos con fases orientacionalmente desordenadas. La imposibilidad de explicar las causas del gran aumento del tiempo de relajación al enfriar un líquido, constituye uno de los problemas más importantes no resueltos en materia condensada. Con el objetivo de dar respuesta a dicha interrogante, se han propuesto modelos termodinámicos y dinámicos que han resultado inconsistentes. En esta tesis nos centramos en dicha problemática, estudiando la dinámica orientacional de algunos materiales que al ser enfriados pueden conservar un orden traslacional mientras que se conserva el desorden orientacional de las moléculas que los forman. Dichas fases se conocen como fases plásticas u orientacionalmente desordenadas (OD). El trabajo presentado en esta tesis amplía el conocimiento de la dinámica de dichas fases, un tema de investigación cuyo interés ha aumentado durante las últimas décadas. Se ha dedicado una atención especial a las ecuaciones fenomenológicas que describen la dependencia del tiempo de relajación con la temperatura. El estudio se ha llevado a cabo mediante el uso de espectroscopía dieléctrica de banda ancha, así como mediante el uso de técnicas experimentales complementarias. Se ha introducido un nuevo método para el estudio de la dinámica de los sistemas que dan lugar a fases vítreas. El método ha sido validado y discutido. Los resultados de esta tesis se presentan divididos en dos temas, por un lado, la dinámica de compuestos puros y de los cristales mixtos y, por otro, el análisis mediante el método derivativo aplicado a los diferentes modelos físicos existentes. En el primer tema nos centramos en la dinámica de los compuestos puros y los cristales mixtos formados por cicloheptanol y ciclooctanol, así como la dinámica de la relajación alfa en 1-ciano-adamantano y sus mezclas con 1-cloro-adamantano. El segundo tema se divide en dos grupos de modelos, los modelos lineales y no lineales. En los modelos lineales se muestra la aplicación del procedimiento de derivativo en los cristales líquidos (CL) y las fases OD. También se discuten los resultados relativos a los casos de la resina líquida (EPON828), la mezcla neopentil-alcohol y neopentil-glicol, el carbonato de propileno, así como el CL isooctilcianobifenil. Se discute también la existencia de posibles correlaciones empíricas entre uno de los modelos lineales con el patrón universal para la parte de alta frecuencia de la curva de pérdidas dieléctricas de la relajación primaria para las fases CL y OD. En la parte final se muestra que la forma de la ecuación introducida recientemente por Mauro et al. no permite la linearización mediante el método derivativo. A diferencia de los modelos anteriores, los diferentes parámetros no están correlacionados con la pendiente y el origen de coordenadas de una función lineal. Para resolver este problema, hemos introducido el concepto del espacio entálpico. Se analiza también la existencia de cambios de comportamiento dinámicos y se aportan descripciones cuantitativas. Se muestra también un nuevo procedimiento para detectar los cambios dinámicos de una manera fácil, que permite incluso detectar aquéllos que son obviados mediante el método clásico de Stickel.

  • Dimorphism of the Produg L-Tyrosine Ethyl Ester: Pressure-Temperature State Diagram and Crystal Structure of Phase II

     Rietveld, Ivo B.; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Nicolaï, Beatrice; Van de Streek, J.; Mahé, Nathalie; Céolin, René; Do, Bernard
    Journal of pharmaceutical sciences
    Date of publication: 2011-06-22
    Journal article

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  • Universal critical-like scaling of dynamics in plastic crystals

     Martinez Garcia, Julio Cesar; Tamarit Mur, Jose Luis; Rzoska, S.J.; Droz-Rzoska, Aleksandra; Pardo Soto, Luis Carlos; Del Barrio Casado, Maria
    Journal of non-crystalline solids
    Date of publication: 2011-01-15
    Journal article

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    Many theoretical models for the glassy dynamics have been proposed so far describing the changes in molecular dynamics along the extraordinary slowing down in the vitrification process of a disordered phase on cooling. Many of these theories share the concept of cooperative rearranging regions firstly proposed by Adam and Gibbs. Among them, the dynamical scaling model (DSM) is based on the random diffusion of free volume which creates random walking clusters formed by cooperatively rearranging entities. Within this framework a critical phenomenon relating a hidden phase transition at TC (below Tg) implies the divergence of the relaxation time (τ) or viscosity (η) τ, η ∝ (T − TC) − phi with a universal scaling exponent φ → 9. In this work we apply the DSM model to orientational glasses, obtained from the quenching of orientationally disordered phases (plastic crystals) via the application of the linearized derivative-based transformation of dielectric spectroscopy τ(T) data.

  • Enantiomer resolution by pressure increase: inferences from experimental and topological results for the binary enantiomer system (R)- and (S)-mandelic acid

     Rietveld, Ivo B.; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Do, Bernard; Céolin, René
    Journal of physical chemistry B
    Date of publication: 2011-11-02
    Journal article

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    In pharmacy, racemic compounds are often problematic, because generally only one of the enantiomers possesses therapeutic activity and it is often difficult to separate them. Even though this problem is likely as old as the pharmaceutical industry, one thermodynamically obvious way of separating racemic crystals has never been studied experimentally, which is by using pressure. Data have been obtained on the equilibria of the (R)- and (S)-mandelic acid system as a function of pressure and temperature. With the use of thermodynamic arguments including the Clapeyron, Schr€oder, and Prigogine Defay equations, it has been demonstrated that the conglomerate (crystals of separated enantiomers) becomes more stable than the racemic compound at approximately 0.64 GPa and 460 K. Even though this pressure is still higher than at the bottom of the Mariana Trench, there are no technical obstacles to produce such conditions, making pressure a viable option for separating enantiomers.

  • Interplay between intramolecular and intermolecular structures of 1,1,2,2-tetrachloro-1,2-difluorethane

     Rovira Esteva, Muriel; Murugan, A.; Pardo Soto, Luis Carlos; Busch, S.; Tamarit Mur, Jose Luis; Pothoczki, Sz.; Cuello, G. J.; Bermejo, F.J.
    Physical review B: condensed matter and materials physics
    Date of publication: 2011-08-18
    Journal article

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  • Secondary relaxations of orientationally disordered mixed crystals at temperatures lower than the glass transition temperature

     Martinez-Garcia, Julio C.; Tamarit Mur, Jose Luis; Pardo Soto, Luis Carlos; Del Barrio Casado, Maria; Rzoska, S. J.; Drozd-Rzoska, A.
    Physica status solidi A. Applications and materials science (Print edition)
    Date of publication: 2011-06-16
    Journal article

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  • Enthalpy space analysis of the evolution of the primary relaxation time in ultraslowing systems

     Martinez Garcia, Julio Cesar; Tamarit Mur, Jose Luis; Rzoska, S.J.
    Journal of chemical physics
    Date of publication: 2011-01-14
    Journal article

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  • Fitting in a complex x2 landscape using an optimized hypersurface sampling

     Pardo Soto, Luis Carlos; Rovira Esteva, Muriel; Busch, S.; Moulin, J.F.; Tamarit Mur, Jose Luis
    Physical review E: statistical, nonlinear, and soft matter physics
    Date of publication: 2011-10-25
    Journal article

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  • Microscopic structures and dynamics of high- and low-density liquid trans-1,2-dichloroethylene

     Rovira Esteva, Muriel; Murugan, Natarajan Arul; Pardo Soto, Luis Carlos; Busch, S.; Ruiz Martin, Maria Dolores; Appavou, M.S.; Tamarit Mur, Jose Luis; Smuda, C.; Unruh, T.; Bermejo, F.J.; Cuello, G. J.; Rzoska, S. J.
    Physical review B: condensed matter and materials physics
    Date of publication: 2010-03-08
    Journal article

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  • Liquid-liquid miscibility gaps and hydrate formation in drug-water binary systems: Pressure-temperature phase diagram of lidocaine and pressure-temperature-composition phase diagram of the lidocaine-water system

     Ceolin, R.; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Veglio, Nestor Raul; Perrin, Marc Antoine; Espeau, Ph.
    Journal of pharmaceutical sciences
    Date of publication: 2010-06-01
    Journal article

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    The pressure–temperature (P–T) melting curve of lidocaine was determined (dP/dT¼3.56MPaK 1), and the lidocaine–water system was investigated as a function of temperature and pressure. The lidocaine–water system exhibits a monotectic equilibrium at 321K (ordinary pressure) whose temperature increases as the pressure increases until the two liquids become miscible. A hydrate, unstable at ordinary pressure, was shown to form, on increasing the pressure, from about 70MPa at low temperatures (200–300 K). The thermodynamic conditions of its stability were inferred from the location of the three-phase equilibria involving the hydrate in the lidocaine–water pressure–temperature–mole fraction (P–T–x) diagram.

  • a-relaxation dynamics of orientationally disordered mixed crystals composed of Cl-adamantane and CN-adamantane

     Martinez Garcia, Julio Cesar; Tamarit Mur, Jose Luis; Capaccioli, Simone; Del Barrio Casado, Maria; Veglio, Nestor Raul; Pardo Soto, Luis Carlos
    Journal of chemical physics
    Date of publication: 2010-04-29
    Journal article

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    The α-relaxation dynamics of 1-cyano-adamantane (CNA) and its mixtures with 1-chloro-adamantane (ClA) has been studied by means of broadband dielectric spectroscopy. The existence of orientationally disordered (OD) face centered cubic mixed crystals (ClA1−XCNAX) for 0.5 ≤ X ≤ 1 has been put in evidence by thermodynamics and structural analyses. In addition to the OD phase of CNA, mixed crystals with compositions higher than the equimolar one exhibit a freezing of the orientational degrees of freedom into a glassy state, which involves also a strong increase of the antiferroelectric order at temperatures higher than the dielectric glass transition temperature. This experimental evidence is revealed by a stairlike effect in the variation of the Kirkwood factor with the temperature as a consequence of a twin effect in the dielectric strength without any anomaly in the temperature-density curves. The characteristic relaxation times are analyzed as a function of temperature and mole fraction. By setting a common temporal origin ("isochronal origin") at τ(Tg) = 100 s for each mole fraction, it emerges that the substitution of ClA molecules by those of CNA (diminution of X) gives rise to a slow down in the dynamics, despite that the molecular volume of ClA molecules are smaller than those of CNA. This fact goes along and is accompanied by a diminution of the lattice packing with the decrease of composition. It is also shown that the heterogeneities produced by the concentration fluctuations due to the chemical disorder are the main contribution to the non-exponential character of the α-relaxation peaks.

  • Disorder effects on heat transport properties of orientationally disordered crystals

     Sharapova, I.V.; Krivchikov, A.I.; Korolyuk, O.A.; Jezowski, A.; Rovira Esteva, Muriel; Tamarit Mur, Jose Luis; Pardo Soto, Luis Carlos; Ruiz Martin, Maria Dolores; Bermejo, F.J.
    Physical review B: condensed matter and materials physics
    Date of publication: 2010-03-30
    Journal article

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  • Evidence for critical-like behavior in ultraslowing glass-forming systems

     Drozd-Rzoska, A.; Rzoska, S.J.; Pawlus, S.; Martinez Garcia, Julio Cesar; Tamarit Mur, Jose Luis
    Physical review E: statistical, nonlinear, and soft matter physics
    Date of publication: 2010-09-10
    Journal article

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  • Disentangling the secondary relaxations in the orientationally disordered mixed crystals: cycloheptanol plus cyclooctanol two-component system

     Martinez Garcia, Julio Cesar; Tamarit Mur, Jose Luis; Pardo Soto, Luis Carlos; Del Barrio Casado, Maria; Rzoska, Syswester J.; Droz-Rzoska, Aleksandra
    Journal of physical chemistry B
    Date of publication: 2010-04-20
    Journal article

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    The dynamics of the pure compounds and mixed crystals formed between cycloheptanol (cC7-ol) and cyclooctanol (cC8-ol) has been studied by means of broadband dielectric spectroscopy at temperatures near and above the orientational glass transition temperature. Both compounds are known to display at least one orientationally disordered (OD) phase of simple cubic symmetry, and within this phase, a continuous formation of mixed crystals was demonstrated in the past (Rute, M. A. et al. J. Phys. Chem. B 2003, 107, 5914). The dielectric loss spectra of cC7-ol and cC8-ol show, in addition to the well-pronounced α-relaxation peaks with a continuous temperature shift (characteristic of the freezing of the molecular dynamics), secondary relaxations ( β and γ for cC8-ol and γ for cC7-ol) which are intramolecular in nature. The dynamics of several OD mixed crystals was recently studied (Singh, L. P.; Murthy, S. S. N. J. Phys. Chem. B 2008, 112, 2606), and surprisingly enough one of the secondary relaxations was not evidenced. We show here by means of a careful set of measurements for several mixed crystals and of a detailed analysis procedure the existence of the secondary relaxations for the mixed crystals. The results, moreover, doubtless reinforce the physical origin of each of the secondary relaxations.

  • Dynamics of orientationally disordered mixed crystal sharing Cl-adamantane and CN-adamantane

     Martinez Garcia, Julio Cesar; Capaccioli, Simone; Diez Berart, Sergio; Tamarit Mur, Jose Luis; Del Barrio Casado, Maria; Veglio, Nestor Raul; Pardo Soto, Luis Carlos
    Journal of non-crystalline solids
    Date of publication: 2010-01-27
    Journal article

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    Orientationally disordered (OD) mixed crystals formed between cyanoadamantane (CN-A) and chloroadamantane (Cl-A) have been thermodynamically characterized by means of thermal analysis and X-ray diffraction. The dynamics of these OD mixed crystals has been studied by means of broad band dielectric spectroscopy. Results evidence that dynamics of the α-relaxation process associated with the overall molecular tumbling slows down when molecules of CN-A are substituted by molecules of Cl-A.

  • Structure of phase III and polymorphism of (CH3)3 CBr

     Negrier, Philippe; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Veglio, Nestor Raul; Mondieig, Denise
    Crystal growth and design
    Date of publication: 2010-05-05
    Journal article

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    The polymorphism of 2-bromo-2-methyl-propane ((CH3)3CBr) has been investigated by both thermal and X-ray powder diffraction experiments. The long time unknown structure of the low-temperature phase III has been determined by X-ray powder diffraction as orthorhombic Pmn21, with lattice parameters a = 19.1350(4) Å, b = 5.7378(1) Å, and c = 10.9626(2) Å at 180 K, Z = 8 and with an asymmetric unit containing one molecule in a general position and two additional molecules placed in a mirror (Z′ = 1 + 1/2 + 1/2). The phase transitions between the different phases have been characterized at normal pressure as well as at high pressures (up to 300 MPa). From the p−T slopes of the two-phase coexistence lines and density measurements as a function of pressure, the volume variations at the transition points have been obtained and compared with those obtained by means of X-ray powder diffraction at normal pressure. The packing as well as the anisotropy of the intermolecular interactions have been analyzed by means of the thermal-expansion tensor and compared with tert-butyl ((CH3)3CX, X = Cl, CN) related compounds.

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    Giant solid-state barocaloric effect in the Ni-Mn-In magnetic shape-memory alloy  Open access

     Mañosa, Lluís; Gonzalez Alonso, David; Planes, Antoni; Bonot, Erell; Del Barrio Casado, Maria; Tamarit Mur, Jose Luis; Aksoy, Seda; Acet, Mehmed
    Nature materials
    Date of publication: 2010-06-01
    Journal article

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    Solid-state materials showing giant caloric effects near room temperature could provide an alternative to cooling devices based on gas cycles. Strong emphasis has so far been dedicated to caloric effects induced by a magnetic field. It is now demonstrated that a small pressure applied to the compound Ni—Mn–In gives rise to a giant caloric response.

  • Neutron diffraction as a tool to explore the free energy landscape in orientationally disordered phases

     Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis
    Date of publication: 2010-01-08
    Book chapter

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  • A procedure to quantify the short range order of disordered phase

     Pardo Soto, Luis Carlos; Tamarit Mur, Jose Luis
    Date of publication: 2010-01-08
    Book chapter

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  • Pressure-Temperature diagram of d-camphor

     Del Barrio Casado, Maria; Rietveld, I.; Tamarit Mur, Jose Luis; Veglio, Nestor Raul; Ceolin, R.; Espeau, P.
    Journées d'Études des Équilibres entre Phases
    Presentation's date: 2010-03-24
    Presentation of work at congresses

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