Change in the thermophysical properties of BCC iron during isothermal compression

Abstract

Equation of state P(V/V 0, T) and baric dependences of the thermodynamic properties of bcc iron are obtained using the Mie–Lennard-Jones interatomic pair potential and the Einstein model of a crystal without any adjustable parameters. The calculations performed along two isotherms at 300 and 1500 K from P = 0 to 8000 kbar = 800 GPa (i.e., to V/V 0 = 0.5) show good agreement with the experimental data. Baric graphical dependences are obtained for the following properties: isothermal bulk modulus B T and B′(P), isochoric specific heat C v and C v ′ (P), isobaric specific heat C p , thermal expansion coefficient α p and α p ′ (P), and specific surface energy of (100) face σ and σ′(P). Analytical approximations are obtained for baric dependences B′(P), α p (P), and σ′(P). It is shown that, at P → ∞, functions B T (P) and σ(P) for bcc iron change linearly and function α p ′ (P) tends toward zero.