Polymorphism and the crystal structures of InSb at elevated temperature and pressure

Polycrystalline x-ray diffraction data are reported for three high-pressure phases of InSb. InSb-II patterns are indexed on the basis of a body-centered tetragonal lattice with unit cell parameters a=5.810 Å and c=3.136 Å at P∼4.3 GPa and T≳100 °C; a unique space group has not been assigned. Possible space groups and structures have been determined for the other high-pressure phases. Contrary to published results, InSb-III is orthorhombic with a=5.712 Å, b=5.357 Å, c=3.063 Å at 11.5 GPa and room temperature, the space group is either Pmmm or Pmmn, and Z=2. InSb-IV is also orthorhombic with a=2.919 Å, b=5.618 Å, and c=3.066 Å at P=4.4 GPa and room temperature; the space group is Pmm2, and Z=1. Atomic coordinates and appropriate bond angles are also reported.