Role of the M point phonons for the dynamical stability of B2 compounds

Although many binary compounds have the B2 (CsCl-type) structure in the thermodynamic phase diagram, an origin of the dynamical 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 dynamical stability of the B2 compounds lies in whether the lowest frequency phonons around the M point in the Brillouin zone are endowed with a positive frequency, except for VRu. 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.