Theory of the <i>β</i>–<i>γ</i> transition in solid oxygen

We consider a model of “discs and spheres” as a description of γ-O2, in which the nutational motion of the precessing molecules is described in terms of a quantum approach, while the remaining orientational degrees of freedom are described classically. Using a modified Kohin potential, we calculate the constants of the molecular and crystalline fields for the precessing molecules in γ-O2, and we show that their orientational state may be described by a negative value of the order parameter. It is shown that the β-γ transition in solid oxygen is related to a change in sign of the order parameter in the orientational subsystem and may be reduced to a transition of the order–order type.

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