Molecular mode-coupling theory for supercooled liquids: Application to water

TL;DR

This paper extends mode-coupling theory to complex molecular liquids like water, demonstrating its effectiveness in predicting slow dynamics near the glass transition through comparison with molecular dynamics simulations.

Contribution

The authors generalize mode-coupling theory to arbitrarily shaped molecules and validate it against simulations for supercooled water.

Findings

Theory accurately predicts q-vector dependence of nonergodicity parameters.

Good agreement between MCT predictions and molecular dynamics data.

Supports applicability of MCT to network-forming supercooled liquids.

Abstract

We present mode-coupling equations for the description of the slow dynamics observed in supercooled molecular liquids close to the glass transition. The mode-coupling theory (MCT) originally formulated to study the slow relaxation in simple atomic liquids, and then extended to the analysis of liquids composed by linear molecules, is here generalized to systems of arbitrarily shaped, rigid molecules. We compare the predictions of the theory for the $q$-vector dependence of the molecular nonergodicity parameters, calculated by solving numerically the molecular MCT equations in two different approximation schemes, with ``exact'' results calculated from a molecular dynamics simulation of supercooled water. The agreement between theory and simulation data supports the view that MCT succeeds in describing the dynamics of supercooled molecular liquids, even for network forming ones.