A system of planar rotators representing H2s and D2s molecules is investigated quantum-statistically, using the mean-field approximation based on an eight-sublattice model. The equilibrium molecular orientation is determined by competition among the dipole-dipole interaction between guest molecules, the host-guest interaction and the quantum kinetic energy. The system has a complex order parameter describing an average direction of dipoles. Both Rl and R3 structures and the effect of the depolarization field are studied. A comparison with experiment by use of theoretical phase diagrams gives: the low-temperature phase has the Rl structure with an antiferroelectric order of dipoles; the direction and arrangement of dipoles in equilibrium for H2S significantly differ from those for D2S because of the quantum nature of the rotational motion.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)