BROKEN SYMMETRY PHASE-TRANSITION IN SOLID HD - A MANIFESTATION OF QUANTUM ORIENTATIONAL MELTING

Theoretical study of the broken symmetry phase (BSP) transition line i n solid HD reveals that its anomalous features provide evidence for qu antum orientational melting. The observations of unusual reentrant beh avior is a consequence of the symmetry properties of the system, namel y, the fact that in HD all rotational states and transitions between t hem are allowed, in contrast to the behavior of the homonuclear isotop es H-2 and D-2. The systematic underestimation of the transition press ure characteristic of all theories of the BSP transition can be remove d if crystal-field effects are taken into account. (C) 1998 American I nstitute of Physics. [S1063-777X(98)01307-3].