Espalhamento Raman do LiCsSO4 a pressão ambiente e a altas pressões

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

Polarized Raman spectra of single crystals of LiCsSO4 were obtained in geometries chosen to allow for the observation of all the Raman active modes. It was found that an isolated factor group analysis fails to give a consistent interpretation of the spectra. Therefore, a complementary calculation, based on a group theoretical method, was employed to obtain the relative intensities for all the internal modes. The calculation was performed by taking the Raman tensors of the free ion transformed to account for the relative orientation of the ion in the crystal. The calculated values compared to the integrated intensities obtained experimentally resulted in good agreement for most of the modes. The lack of some modes in the spectra was explained based in this theoretical model. The Raman spectra of LiCsSO4 was also studied for pressures varying in the range 1 atm to 7 GPa. The spectra were observed to change qualitatively when the pressure attains the value 3.8 GPa. The modification was rapid and reversible. The plots of frequency versus pressure showed marked discontinuities at P = 3.8 GPa, changes were interpreted here as evidences of reversible structural phase transition occurring in lithium cesium sulfate at Pc = 3.8 GPa. The characteristics of this transition were seen to be consistent with a polyhedral tilt transition

ASSUNTO(S)

efeito de raman espalhamento (fisica)

ACESSO AO ARTIGO

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