The Origin of Persistent Shear Stress in Supercooled Liquids

We show that the long time tail of the shear stress autocorrelation, whose growth at large supercooling is responsible for the apparent divergence of the shear viscosity, is a direct result of a residual shear stress in the structures associated with the local potential minima. We argue that the essential mechanical transition experienced by a liquid on cooling occurs at a temperature well above the glass transition temperature and corresponds to the crossover from the high temperature liquid to the viscous liquid, the latter characterised by stress relaxation dominated by the residual stress. Following on from this observation, as the density is decreased, the local potential minima become unable to sustain any persistent stress (and, hence, support a glass transition), in a manner that can be explicitly connected to the interactions between atoms. The reported crossover implies an associated change in the mechanism of dissipation in liquids and, hence, raises the prospect of a coherent microscopic treatment of nonlinear rheology and the relationship between self diffusion and viscosity in supercooled liquids

From Liquid Structure to Configurational Entropy: Introducing Structural Covariance

We connect the configurational entropy of a liquid to the geometrical properties of its local energy landscape, using a high-temperature expansion. It is proposed that correlations between local structures arises from their overlap and, being geometrical in nature, can be usefully determined using the inherent structures of high temperature liquids. We show quantitatively how the high-temperature covariance of these local structural fluctuations arising from their geometrical overlap, combined with their energetic stability, control the decrease of entropy with decreasing energy. We apply this formalism to a family of Favoured Local Structure (FLS) lattice models with two low symmetry FLS's which are found to either crystallize or form a glass on cooling. The covariance, crystal energy and estimated freezing temperature are tested as possible predictors of glass-forming ability in the model system

Favoured Local Structures in Liquids and Solids: a 3D Lattice Model

We investigate the connection between the geometry of Favoured Local Structures (FLS) in liquids and the associated liquid and solid properties. We introduce a lattice spin model - the FLS model on a face-centered cubic lattice - where this geometry can be arbitrarily chosen among a discrete set of 115 possible FLS. We find crystalline groundstates for all choices of a single FLS. Sampling all possible FLS's, we identify the following trends: i) low symmetry FLS's produce larger crystal unit cells but not necessarily higher energy groundstates, ii) chiral FLS's exhibit to peculiarly poor packing properties, iii) accumulation of FLS's in supercooled liquids is linked to large crystal unit cells, and iv) low symmetry FLS's tend to find metastable structures on cooling.Comment: 11 pages, 6 figure