DSC, X-RAY-DIFFRACTION AND RAMAN STUDIES IN THE 2-DIMENSIONAL COMPOUND CH3NH3HGCL(CN)(2)

The Raman spectra (10 to 500 cm(-1)), X-ray diffraction and differenti al scanning calorimetry of polycrystalline samples of CH3NH3HgCl(CN)(2 ) were investigated in the temperature range 300 to 400 K. This work s hows a second-order phase transition at 353 K. The room-temperature ph ase is ordered and exhibits monoclinic symmetry (space group P2/m with a = 13.0544(10) Angstrom, b = 4.1549(10) Angstrom, c = 13.7512(10) An gstrom, beta = 93.32 degrees, Z = 4). The high-temperature phase is di sordered and seems to have a monoclinic cell symmetry (a = 18.499(6) A ngstrom, b = 4.782(2) Angstrom, c = 18.109(7) Angstrom, beta = 94.72 d egrees, Z = 8).