Orientational ordering: Computer studies of the quadrupolar "glass"

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Abstract
The electric quadrupole-quadrupole model for orientational ordering on the rigid hcp lattice is studied with the use of standard computer-simulation techniques. Appropriate order parameters, which isolate various symmetries, are used to describe this system. It is found that several distinct admixtures of the long-range-ordered states are degenerate at and below the phase transition. The zero-temperature state appears to consist of randomly stacked ordered planes, and the ordering appears to be mediated by the presence of excitations of the "wrong" symmetry. Although the form of the zero-temperature order parameter appears to depend on the annealing schedule used, the observed susceptibilities do not.