On the surface energy of crystals of inert gases

Abstract

The dependences of the specific surface energy (σ) and its isochoric temperature derivative (∂σ/∂T) V on the degree of compression (V/V 0) of the crystal are calculated on the basis of the Mie-Lennard-Jones pair potential of interatomic interaction. The calculations are performed for all face-centered cubic crystals of inert gases (from Ne to Rn) to the degree of compression V/V 0 = 0.016 along three isotherms: 1K, T m and 300 K, where T m is the melting temperature at zero pressure (V/V 0 = 1). The activation processes such as the creation of vacancies and self-diffusion are taken into account in the calculations. It is shown that the isotherm σ(V/V 0) reaching its maximum at (V/V 0)max sharply decreases upon further compression. The surface energy becomes negative (σ(V/V 0) fr =0) at V/V 0 ≤ (V/V 0) fr < (V/V 0)max which should stimulate the process of crystal fragmentation, i.e., an increase in the specific (per atom) intercrystallite surface. It is shown that at high temperatures the condition of fragmentation holds in the crystal in the case of uniform tension, but it is already in the region of the liquid phase. The values of σ, (∂σ/∂T) V , the vacancy concentration and the fraction of the diffusion atoms are estimated at the points: V/V 0 = 1, (V/V 0)max and (V/V 0) fr at 1 K, Tm and 300 K. The size evolution of the surface and activation parameters is studied using neon as an example.