Raman spectra of an oriented crystal of anhydrous Li2SO4are reported in the temperature range 25ndash;775thinsp;deg;C which includes the monoclinichyphen;fcc phase transition at 575thinsp;deg;C. Qualitative differences in the general spectra in the two solid phases are discussed. A quantitative analysis has been carried out for the internal ngr;1band of the SO2minus;4ions, the high frequency component of the ngr;2band, and the lithium lattice modes, both inBgand inAgsymmetry. The broadening and frequency shift of the ngr;1band are discussed in the light of current theories. In the lsquo;lsquo;pretransitionalrsquo;rsquo; range belowTcthe frequency of ngr;1seems to exhibit critical behavior with the exponent equal to 1/6. A temperaturehyphen;dependent coupling between lithium modes and the high frequency component of the ngr;2band is revealed by analysis of the temperature dependence of the frequency and bandwidth of both modes inBgsymmetry. Comparison is made with similar phenomena in other lithiumhyphen;containing sulfate crystals.
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