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AbslracL Raman xattering investigations of lithium polasium sulphate at high pressures have revealed l h a l the sulphate tetrahedra are orientationally disordered in the highpressure phases. I n order la understand the nature of lhe disorder, the lemperature dependence of the relative intensities of Raman lines associaled with lhe sulphale inlernal mnds are investigated. l l~l h e resulls suggest a frozen-in static disorder rather lhan dynamic equilibrium between the acupancics of different orientations The behaviour of lhe Raman linewidths up to a preuure of 2. 50 kbar indicates sucassively broader distributions of the sulphate orientations. A mechanism of amorphization involving disorder in cation sublattices induced the orientational disorder of sulphate is proposed.

We show, using the Mandelstam-Leibbrandt prescription, that the difference between linearly divergent integrals in the light cone gauge leads to surface terms which diverge logarithmically. We discuss the origins and implications of such a divergence.