X-ray diffraction study of a sequence of phase transitions in Cs2HgCl4 crystals

The temperature behavior of lattice parameters and diffraction patterns of the reciprocal lattice in Cs2HgCl4 crystals is studied by x-ray diffraction in the temperature range from 4.2 to 300 K. A sequence of phase transitions is observed and attributed to the evolution of incommensurate and commensurate modulations along the crystallographic a and c axes of a unit cell in the initial Pnma structure.