This project continues the work of two long-experience, complementary and scientifically contrasted research groups working within the framework of glass-forming (organic and metallic) materials, sharing knowledge and available equipment and strengthening the international reputation. The understanding of the behavior of non-crystallizing liquids and the formation of glasses by decreasing temperature (or increasing pressure) is an unsolved problem currently seen as a major intellectual challenge in condensed matter physics. The initial concept of glassy state has now been generalized and it is recognized that any system with some kind of disorder (translational, orientational, conformational, statistical disorder of site occupancy, ) in its ergodic state can give rise to a glassy state, the non-ergodic state (by cooling, by pressurizing or by other physical methods as vapor deposition) in which the initial degrees of freedom become frozen. The so-reached amorphous states in simple organic compounds, polymers, ceramics, and metallic systems provide a variety of important materials which are, in many cases, of widespread use. The glass transition is a kinetic phenomenon and hence the properties of glasses depend on the thermodynamic path to reach the glass state. The importance of dynamics, one of the main topics of this project, becomes obvious when considering the usual way of preparing a canonical glass: a liquid has to be cooled sufficiently fast to avoid crystallization. Thus, the key points for understanding the glass transition concern the physics behind the continuous and dramatic increase of the shear viscosity, or similarly, the main (collective) structural alfarelaxation time, the origin of the secondary fast beta-relaxations and the dynamic heterogeneities embedded into the intermediate scattering function, F_S(q, t), providing a general connection between spatial fluctuations and relaxation kinetics. Alike crystalline solids share many properties regardless their composition, glasses show very similar responses to different types of perturbations, independently of the materials details. Such universalities enable us to treat simple molecular compounds or atomic metallic glass-formers within equivalent physical images and, hence, sharing the knowledge between members of the present group working on apparently different kind of glass-forming materials. The project will mainly deepen on the links between the dynamics phenomena and structural features of the canonical (i.e. structural), organic and metallic, glasses (obtained by freezing the whole disorder of the liquid state), orientational glasses (obtained by freezing the orientational disorder, in plastic phases) and low-dimensional glasses (obtained by freezing the statistical disorder on the site occupancy in low-symmetry lattices). The influence of pressure in the dynamics of glasses will be one of the differentiating facts with respect to other research groups. From the use of temperature- and pressure-dependent measurements, it is possible to unravel whether the molecular dynamics is dominated (limited) by thermal energy or by the available free volume. In addition, combination of both variables allows disentangling the two competitive driving forces having critical influence on the crystallization process, i.e. kinetics (nucleation and growth) and thermodynamics (chemical potential difference).
Valenti, S.; Romanini, M.; Franco, L.; Puiggali, J.; Tamarit, J. Ll.; Macovez, R. Molecular pharmaceutics Vol. 15, num. 12, p. 5615-5624 DOI: 10.1021/acs.molpharmaceut.8b00786 Date of publication: 2018-10-23 Journal article
Pitta, S.; Roure, F.; Crespo, D.; Rojas, J.I. International Conference on Composite Structures p. 1-26 DOI: 10.15651/978-88-938-5079-7 Presentation's date: 2018-09-05 Presentation of work at congresses
Tamarit, J. Ll.; Romanini, M.; Macovez, R.; Del Barrio, M.; Pardo, L. 10th Conference on BroadBand Dielectric Spectroscopy and its Applications p. O-54 Presentation's date: 2018-08-29 Presentation of work at congresses
Pitta, S.; Rojas, J.I.; Crespo, D.; Wahab, M. A. International Conference on Fracture Fatigue and Wear p. 558-565 DOI: 10.1007/978-981-13-0411-8_50 Presentation's date: 2018-07-09 Presentation of work at congresses