Instability of the high-pressure CsCl structure in most III-V semiconductors

Using the density-functional linear response method, we study dynamical instabilities of the high-pressure CsCl phase in III-V semiconductors. For InSb, we find no phonon instability that could prevent the CsCl phase from forming, consistent with the experimental observation. In contrast, for the more ionic GaP, GaAs, InP, and InAs, we find that, while statically stable, the CsCl phase is dynamically unstable at high pressures with respect to transverse-acoustic [xi xi 0] phonons. Analysis of the soft normal modes via "isotropy subgroup" suggests two candidate structures that will replace CsCl structure at high pressure: the tP4 (B10) InBi type and the oP4 (B19) AuCd type. Experimental examination of these predictions is called for.