Issue
EPL
Volume 81, Number 4, February 2008
Article Number 40007
Number of page(s) 5
Section General
DOI http://dx.doi.org/10.1209/0295-5075/81/40007
Published online 23 January 2008
EPL, 81 (2008) 40007
DOI: 10.1209/0295-5075/81/40007

Phase field crystals as a coarse-graining in time of molecular dynamics

P. F. Tupper1 and M. Grant2

1  Department of Mathematics and Statistics, McGill University - Canada
2  Department of Physics, McGill University - Canada


received 9 July 2007; accepted in final form 21 December 2007; published February 2008
published online 23 January 2008

Abstract
Phase field crystals (PFC) are a tool for simulating materials at the atomic level. They combine the small length scale resolution of molecular dynamics (MD) with the ability to simulate dynamics on mesoscopic time scales. We show how PFC can be interpreted as the result of applying coarse-graining in time to the microscopic density field of molecular-dynamics simulations. We take the form of the free energy for the phase field from the classical density functional theory of inhomogeneous liquids and then choose coefficients to match the structure factor of the time coarse-grained microscopic density field. As an example, we show how to construct a PFC free energy for Weber and Stillinger's two-dimensional square crystal potential which models a system of proteins suspended in a membrane.

PACS
05.70.Ln - Nonequilibrium and irreversible thermodynamics.
64.70.Dv - Solid-liquid transitions.
61.50.Ah - Theory of crystal structure, crystal symmetry; calculations and modeling.

© EPLA 2008