IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
GLASSY DYNAMICS IN “ORDERED” PHASES
Autor/es:
J. LL. TAMARIT; L.C. PARDO; M. ROMANINI; M. ZURIAGA; S. CAPACCIOLI; M. BARRIO; P. LUNKENHEIMER; A. LOIDL
Lugar:
Sendai
Reunión:
Congreso; 5th International Discussion Meeting on Glass Transition; 2012
Institución organizadora:
Institute of Fluid Science, Tohoku University
Resumen:
The most common glass formers obtained for a wide variety of systems result from the freezing of translational and rotational degrees of freedom [1,2]. Nevertheless, systems in which the centers of mass of molecules form a long-range ordered lattice with orientationally degrees of freedom (plastic phases) can be supercooled giving rise to an orientational glass [3,4]. The degree of disorder can be further decreased and the features characterizing a glass can still survive [5]. Some representative examples of these systems will be presented and their properties compared to those of canonical glasses. The systems we are dealing with concern the monoclinic low-temperature phase of tetrahedral (rigid) molecules (CBrnCl4-n, n= 0, 1, 2) where an intrinsic disorder appears linked to the occupational disorder of the halogen sites within the asymmetric unit (Z’=4). An additional kind of systems refers to the low-temperature phase of 2-adamantanone rigid molecule, in which the oxygen atom also lies in 3 non-equivalent occupational sites within the asymmetric unit. In these “ordered” systems 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. Thus, for both set of systems, a slower (-) and a faster (-) relaxation processes appear, as for many canonical glasses. On the contrary, we will highlight that the similar apparent experimental results concerning the existence of both primary and secondary relaxations correspond to different physical microscopic mechanisms.