Homogeneous Periodic Heat Flow via NonequiIibrium Molecular Dynamics*

Two non equilibrium methods for simulating homogeneous periodic heat flow are applied to 108 three-dimensional soft spheres in both the fluid and face centered cubic;>olic-,phases. Both nonequilibrium methods use irreversible.ther· modynamics to"express heat conductivity in terms of the work required to generate heal £1ow. The Evans-Gillan method, derived from Green-Kubo theory. correctly reproduces Ashurst', heat conductivities. An appro:lch based on Gauss ' principle of least constraint, in which the heat flow is constrained to a flxed value, fails this rest. Heat flow is an inhomogeneous, nonlinear function of particle velocities and coordinates. Thus. Gauss ' principle cannot be relied upon for treating inhomogeneous nonlinear nonholonomic constraints. KEY WORDS: Nonequilibrium; molecular dynamics; conductivity; heat flow; irre\'ersible thermodynamics: steady state