Structural (B1 to B8) Phase Transition in MnO under Pressure: Comparison of All-electron and Pseudopotential Approaches

TL;DR

This study compares all-electron and pseudopotential methods in predicting the pressure-induced B1 to B8 phase transition in MnO, highlighting differences in accuracy and transferability issues.

Contribution

It provides a detailed comparison of computational approaches for MnO's phase transition, emphasizing the limitations of pseudopotentials in high-pressure simulations.

Findings

All-electron and pseudopotential methods yield significantly different quantitative results.

Small-core pseudopotentials show transferability inaccuracies for spin polarization energies.

Both approaches can predict the transition but differ in precision and reliability.

Abstract

We employ the density functional theory to study a structural transition of MnO from B1 (rocksalt) to B8 (NiAs) structures that was observed experimentally at pressures around 100 GPa. We utilize all-electron description as well as norm-conserving pseudopotentials and demonstrate that these two approaches can significantly differ in quantitative predictions. We explicitly show that even small-core pseudopotentials exhibit transferability inaccuracies for quantities sensitive to the energy differences between high- and low-spin polarizations of valence electrons.