TRANSIENT FOURIER-LAW DEVIATION BY MOLECULAR-DYNAMICS IN SOLID ARGON

Using a molecular-dynamics (MD) numerical simulation, we test the vali dity of the generalized Fourier law predicted by Cattaneo and Vernotte (CN) and theoretically established in the extended irreversible therm odynamics. The numerical experiments are achieved at constant and high density in a Lennard-Jones (6-12) solid argon. The temperature domain is restricted to the so-called kinetic region where the thermal condu ctivity lambda-T-1. it was found that the heat flux relaxation time ta u(V) and the phonon mean relaxation time are numerically equal with a good accuracy, in agreement with the consequence of the phonon transfe r equation at macroscopic equilibrium; For nonequilibrium regimes, we study the thermal response of the lattice to a temperature disturbance of low or high magnitude, Stress effects were detected and excluded f rom the kinetic temperature measurement. Finally, a thermal energy ana lysis shows that the time transition to the Fourier regime is well pre dicted by the MD value of tau(V), but a large disagreement is found be tween the MD data and the hyperbolic model solution before that time. As a conclusion, the CV law is confirmed when considering heat Aux flu ctuations at equilibrium, but nonequilibrium situations with macroscop ic temperature gradients are badly represented by the hyperbolic model .