Stability of B2 compounds: Role of the $M$ point phonons

TL;DR

This study investigates the dynamical stability of B2-structured binary compounds, revealing that stability depends on the positive frequency of phonons at the M point and the importance of up to fourth nearest neighbor interactions.

Contribution

It identifies the critical role of M point phonons in B2 phase stability and establishes the necessary cutoff radius for interatomic potential modeling.

Findings

B2 phase stability correlates with positive M point phonon frequencies.

Interatomic interactions up to the fourth nearest neighbor are essential for stability.

Provides criteria for constructing accurate interatomic potentials.

Abstract

Although many binary compounds have the B2 (CsCl-type) structure in the thermodynamic phase diagram, an origin of the structural stability is not understood well. Here, we focus on 416 compounds in the B2 structure extracted from the Materials Project, and study the dynamical stability of those compounds from first principles. We demonstrate that the B2 phase stability lies in whether the lowest frequency phonon at the $M$ point in the Brillouin zone is endowed with a positive frequency. We show that the interatomic interactions up to the fourth nearest neighbor atoms are necessary for stabilizing such phonon modes, which should determine the minimum cutoff radius for constructing the interatomic potentials of binary compounds with guaranteed accuracy.