Orientational Glasses and High Pressure Phases Studied by NMR

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The nature of freezing in orientational glasses is as yet an open question. The proposed experimental work will investigate whether the freezing is random. Temperature-jump nuclear magnetic resonance will be employed to determine whether individual molecules return to the same orientation upon repeated melting and freezing. The experiments will use the well-studied orientational glasses potassium cyanide-bromide and sodium- potassium cyanide. The experiments should lead to a more detailed understanding of the glassy state of matter. Studies of simple molecular solids at high pressures have found new solid phases. However, almost none of the work to date has studied the dynamics of these solids. In particular, it is not known whether the orientational disorder in the high pressure disordered phases is static or dynamic. Nuclear magnetic resonance in diamond anvil cells, a recently developed technique, will be used to study the orientational dynamics. Diffusion will also be measured to look for a change in mechanism at high densities. The work will begin with nitrogen and carbon monoxide because reliable phase diagrams are available and because of their molecular similarities. The work should extend the understanding of high density materials.