From orientational glasses to structural glasses: What computer simulations have contributed to understand experiments

Orientational glasses, produced by random dilution of molecular crystals, exhibit a freezing transition of the quadrupole moments. Monte Carlo simulations of lattice models (generalization of the Edwards-Anderson spin glass model) have been used to elucidate this behavior. While short range models exhibit a static glass transition at zero temperature only, the infinite range Potts glass exhibits a transition where a glass order parameter appears discontinuously. At higher temperature, a dynamical transition occurs, described by mode-coupling theory (MCT). MCT has also been tested by Monte Carlo and molecular dynamics simulations of coarse-grained models of glass-forming polymers. While these simulations have clarified some debated theoretical issues and helped to interpret experiments, still fascinating questions about the character of the glass transition remain unanswered. These efforts to clarify the glass transition by computer simulation are briefly reviewed, and the current status is summarized. (C) 2002 Elsevier Science B.V. All rights reserved.