We argue that activated motions in dense liquids can be mapped onto the dynamics of a six-component Heisenberg model, whereby the dynamical variables are the components of the tensor reflecting local frozen-in deformation relative to a periodic reference state. The multiplicity of distinct spin configurations corresponds to the structural degeneracy of the liquid. The spin model exhibits a continuous range of behaviors between two limits corresponding to frozen-in shear and uniform compression/dilation respectively. The two regimes are separated, in the mean field limit, by a continuous transition controlled by the anisotropy in the spin-spin interaction, which is controlled by the Poisson ratio of the material. The liquid's fragility is argued to depend on the Poisson ratio in a non-monotonic way. The present approach provides a framework for estimating the configurational entropy and relaxational spectrum of actual substances. Numerical solution of the model in finite dimensions is presented.

Activated transport in supercooled liquids mapped onto dynamics of a spin model defined on a fixed lattice

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.