Energy landscape - a key concept for the dynamics of glasses and liquids

TL;DR

This paper discusses the energy landscape concept as a key to understanding the dynamics of glasses and liquids, integrating theories like mode coupling and entropy calculations, and examining relaxation models.

Contribution

It synthesizes various theoretical approaches to the energy landscape, including mode coupling, entropy calculations, and relaxation models, to better understand glass and liquid dynamics.

Findings

Mode coupling theory is a promising microscopic model for undercooled liquids.

Energy landscape saddlepoints relate to the transition to the glassy state.

Interactions among relaxation centers significantly influence the relaxation process.

Abstract

There is a growing belief that the mode coupling theory is the proper microscopic theory for the dynamics of the undercooled liquid above a critical temperature T_c. In addition, there is some evidence that the system leaves the saddlepoints of the energy landscape to settle in the valleys at this critical temperature. Finally, there is a microscopic theory for the entropy at the calorimetric glass transition T_g by Mezard and Parisi, which allows to calculate the Kauzmann temperature from the atomic pair potentials. The dynamics of the frozen glass phase is at present limited to phenomenological models. In the spirit of the energy landscape concept, one considers an ensemble of independent asymmetric double-well potentials with a wide distribution of barrier heights and asymmetries (ADWP or Gilroy-Phillips model). The model gives an excellent description of the relaxation of glasses up to about T_g/4. Above this temperature, the interaction between different relaxation centers begins to play a role. One can show that the interaction reduces the number of relaxation centers needed to bring the shear modulus down to zero by a factor of three.