Tesis doctoral de Ricardo Palomar Polo
The aim of this thesis is the study of supercooled liquids by means of molecular dynamics simulations. We have investigated the behavior of hydrogen bonded liquids, specifically the low weight alcohols methanol and ethanol. In both systems, relaxation times and transport coefficients diverge at a critical temperature. For all correlators under study, a two-step relaxation behavior has been encountered. Translation dynamics of molecular centers-of-mass agrees reasonably well with mode coupling predictions. At low temperatures and intermediate time scales, a remarkable deviation from gaussian dynamics is found. This deviation is related to the existence of dynamical heterogeneities. the role of hydrogen bonding in supercooled methanol has also been analyzed. The results obtained for methanol have been compared with those of an ideal methanol-like system whose diatomic molecules have the same dipole moment as the methanol ones but lack sites for hydrogen bonding. Upon cooling, it has been found that translational relaxation times increase more rapidly than reorientational ones, being this effect more important in the non-associated system. Suppression of hydrogen bonds also results in lower critical temperatures for diffusion and for several characteristic relaxation times. Deviations from gaussian dynamics are more relevant in methanol, but the long time behavior does not depend on the existence of hydrogen bonds. dynamic heterogeneities have been analyzed in the supercooled system of diatomic molecules. Correlations between molecular displacements performed during consecutive time intervals are apparent at low temperatures and intermediate times, whereas they tend to disappear at long times (-relaxation). These correlations maximize when the deviation from gaussian dynamics takes a maximum. The molecular displacement has an important anisotropic component at intermediate time scales (-relaxation). Dynamic heterogeneities in reorientation have been observed at the
Datos académicos de la tesis doctoral «Simulacio per dinamica molecular de liquids moleculars sobrerefredats«
- Título de la tesis: Simulacio per dinamica molecular de liquids moleculars sobrerefredats
- Autor: Ricardo Palomar Polo
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 05/12/2007
Dirección y tribunal
- Director de la tesis
- Gemma Sese Castel
- Tribunal
- Presidente del tribunal: Padro cardenas joan angel
- eudald Vilaseca font (vocal)
- Arbe mendez María aranzazu (vocal)
- Tamarit mur josep lLuis (vocal)