Preprint Article Version 1 This version not peer reviewed

# Nonclassical Symmetry Solutions for 4th Order Phase Field Reaction-Diffusion

Version 1 : Received: 18 January 2018 / Approved: 18 January 2018 / Online: 18 January 2018 (06:44:57 CET)

How to cite: Broadbridge, P.; Triadis, D.; Gallage, D.; Cesana, P. Nonclassical Symmetry Solutions for 4th Order Phase Field Reaction-Diffusion. Preprints 2018, 2018010169 (doi: 10.20944/preprints201801.0169.v1). Broadbridge, P.; Triadis, D.; Gallage, D.; Cesana, P. Nonclassical Symmetry Solutions for 4th Order Phase Field Reaction-Diffusion. Preprints 2018, 2018010169 (doi: 10.20944/preprints201801.0169.v1).

## Abstract

Using a nonclassical symmetry of nonlinear reaction-diffusion equations, some exact multi-dimensional time-dependent solutions are constructed for a fourth-order Allen-Cahn-Hilliard equation. This models a phase field that gives a phenomenological description of a two-phase system near the critical temperature. Solutions are given for the changing phase of a cylindrical or spherical inclusion, allowing for a 'mushy zone' with mixed state that is controlled by imposing a pure state at the boundary. The diffusion coefficients for transport of one phase through the mixture, depend on the phase field value, since the physical structure of the mixture depends on the relative proportions of the two phases. A source term promotes stability of both of the pure phases but this tendency may be controlled or even reversed through the boundary conditions.

## Subject Areas

fourth-order diffusion; Allen-Cahn equation; Cahn-Hilliard equation; phase field; nonlinear reaction-diffusion