Importance of Magnetism in Phase Stability, Equations of State, and Elasticity

TL;DR

This paper explores how magnetism influences the phase stability, equations of state, and elasticity of transition metals and oxides under high pressure, highlighting its crucial role in their physical properties.

Contribution

It provides a comprehensive analysis of magnetic effects on high-pressure properties using advanced computational methods, including LDA+U, and discusses implications for transition metals and oxides.

Findings

Magnetism stabilizes bcc iron at ambient conditions.

Magnetism affects thermal expansivity and elasticity of hcp iron.

LDA+U inhibits high-spin low-spin transitions in oxides.

Abstract

The effects of magnetism on high pressure properties of transition metals and transition metal compounds can be quite important. In the case of Fe, magnetism is responsible for stability of the body-centered cubic (bcc) phase at ambient conditions, and the large thermal expansivity in face-centered cubic (fcc) iron, and also has large effects on the equation of state and elasticity of hexagonal close-packed (hcp) iron. In transition metal oxides, local magnetic moments are responsible for their insulating behavior. LDA+U results are presented for CoO and FeO, and predictions are made for high pressure metallization. The inclusion of a local Coulomb repulsion, U, greatly inhibits the high-spin low-spin transitions found with conventional exchange-correlation functionals (i.e. generalized gradient corrections, GGA). We discuss theory and computations for the effects of magnetism on high pressure cohesive properties.