INFRARED AND RAMAN SPECTRAL STUDIES AND NORMAL-MODES OF ALPHA-BI2O3

Infrared and Raman spectra for alpha-Bi2O3 have been recorded at 300 K and 85 K and analysed in detail. alpha-Bi2O3 belongs to the monoclinic system, to space group P2(1)/c. From the factor group analysis, 60 lattice vibrations are distributed as 15A(g), 15B(g), 15A(u) and 15B(u) modes of the group. The observed IR and Raman frequencies are assigned to the various vibrational modes and an analysis of the lattice vibrations is carried out by the Wilson GF matrix method using a least-squares fit technique. The analysis makes it possible to completely describe the fundamental modes of alpha-Bi2O3 and leads to a force field which can be transferred to other systems containing Bi and O atoms.