Ideal and limiting strength of a Lennard-Jones crystal at temperatures lower than the melting line endpoint temperature: molecular dynamics simulation

Abstract

ABSTRACT The conditions of stability of a stretched face-centered cubic (FCC) crystal against infinitesimal and finite changes in the state parameters have been considered at temperatures lower than that of the endpoint of the melting line [V.G. Baidakov, S.P. Protsenko. Phys. Rev. Lett. 95 015701 (2005)]. Molecular dynamics simulation has been used to calculate effective isothermal elastic moduli, average lifetimes, the work of formation of a critical nucleus and the nucleation rate close to the boundary of the limiting stretching of a Lennard-Jones FCC crystal. States in which the isothermal bulk elastic modulus K is equal to zero, with the shear moduli and being nonzero, have been achieved. It is shown that at K < 0 the crystal retains thermodynamic stability. The kinetics of the phase decay of a Lennard-Jones crystal beyond to the line K = 0 has been investigated. It has been found that the decay proceeds by the nucleation mechanism, through the formation and growth of new-phase nuclei. As distinct from small stretchings, at the boundary of limiting ones the nucleus has a form close to spherical.