Neutron powder diffraction study of (ND4)2SeCl6 under high pressure

The phase transition (T-trs = 48 K) of (ND4)(2)SeCl6, which exhibits a strong isotope effect, has been studied by neutron powder diffraction under high pressure. Data of the high-temperature phase were collected on HRPD at ISIS under helium gas pressure of 480 MPa at 63 K. The Rietveld analysis and Fourier contour map revealed that the D atom of the ND4+ ion is broadly disordered around the C-3-axis of the cubic lattice at lower pressure and tends to be localized on the axis at higher pressure. (C) 1998 Published by Elsevier Science B.V. All rights reserved.