Tetragonal high-pressure phase of InI predicted from first principles

Ab initio particle swarm optimization algorithm for crystal structural prediction was employed to uncover the high-pressure crystal structure of indium iodide (InI). We have predicted one tetragonal high-pressure phase for InI with P4/nmm symmetry, which is energetically much superior to the previously proposed CsCl-type structure. The P4/nmm-InI possesses alternative stacking of double I and In layers. The arrangement of adjacent I and In layers of P4/nmm-InI is similar to that of the CsCl-type structure. The calculated electronic density of states supports a metallic character for this tetragonal phase that is similar to the high-pressure behavior of IIA–VIB families. Furthermore, the phase transition path from the ambient pressure TlI–InI→P4/nmm-InI has been discussed.