Orientational Order Parameter in Solid CD4

Superlattice reflections below the I/II phase transition of solid heavy methane are connected with the orientational ordering that occurs. As a consequence of a temperature-dependent neutron measurement, they may be grouped into two classes, both with structure amplitudes following exponential laws but having different exponents $\beta =0.21\mathrm{}$ and ${\beta }^{\prime }=0.31\mathrm{}$. This experimental behavior is well understood on the basis of a molecular-field-type analysis, which also shows that the system is close to a hypercritical point.