Rhombohedral-to-Triclinic Phase Transition in BaMo sub 6 S sub 8

摘要

The rhombohedral, R3 bar, to triclinic, P1 bar, transition in BaMo sub 6 S sub 8 at 175K has been studied by neutron powder diffraction. The first order nature of the transition, as required by Landau theory, is suggested by the temperature dependence of the triclinic distortion; however, no volume discontinuity can be seen with the precision of this measurement. The triclinic structure is characterized by a distortion of the Mo sub 6 octahedra and a shear of the axial sulfur atoms which allows the Ba ion to localize at the origin position. 6 refs., 4 figs., 1 tab. (ERA citation 10:051849)