High-pressure transitions of trigonal alpha-ZrMo2O8

High-pressure synchrotron x-ray powder-diffraction studies show that trigon al alpha-ZrMo2O8 transforms to a monoclinic symmetry phase (delta-ZrMo2O8) at 1.06-1.11 GPa. The space group was determined to C2/m. A further high-pr essure transition from the monoclinic delta to a triclinic epsilon phase oc cur at 2.0-2.5 GPa (space group P1 or P (1) over bar). Both transformations are reversible. The Volume compressibilities are similar for the alpha and delta phase, and five times lower for the epsilon phase.