Observation of the high-pressure Pmma phase in InAs:: A combined X-ray absorption and diffraction study

X-ray absorption and diffraction measurements on InAs up to 80 GPa reveal the presence of a high-pressure short-range chemically disordered Pmma structure and shows no evidence of the CsCl phase. The combination of the two techniques proved to be essential to fully describe the new phase. Since Pmma symmetry has recently been shown to be a direct consequence of a phonon instability of CsCl, this result highlights recent theoretical calculations that are able not only to identify instabilities in "statically" stable phases, but also to predict the occurrence of alternative symmetries.