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 A and c=3.136 A 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 A, b=5.357 A, c=3.063 A 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 A, b=5.618 A, and c=3.066 A 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.