<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>LDA</mml:mi><mml:mo>+</mml:mo><mml:msub><mml:mi>U</mml:mi><mml:mrow><mml:mi>s</mml:mi><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> calculations of phase relations in FeO
Yang Sun, Matteo Cococcioni, Renata M. Wentzcovitch
Abstract
Using the $\mathrm{LDA}+{U}_{sc}$ method, we present calculation phase relations of iron monoxides involving five polytypes in multiple spin-state configurations. The Hubbard parameter $U$ is determined self-consistently simultaneously with the occupation matrix and structures at arbitrary pressures. The Hubbard parameter strongly depends on pressure, structure, and spin state. Comparison with experimental structural data indicates the $\mathrm{LDA}+{U}_{sc}$ can predict structure, compression curves, phase relations, and transition pressures very well for the insulating $B1$ and iB8 states. However, it requires additional calculations using the Mermin functional that includes the electronic entropic contribution to the free energy to obtain an nB8 metallic state and a consistent iB8 to nB8 insulator to metal transition pressure.