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 monoclini c system, to space group P2(1)/c. From the factor group analysis, 60 l attice vibrations are distributed as 15A(g), 15B(g), 15A(u) and 15B(u) modes of the group. The observed IR and Raman frequencies are assigne d to the various vibrational modes and an analysis of the lattice vibr ations is carried out by the Wilson GF matrix method using a least-squ ares fit technique. The analysis makes it possible to completely descr ibe the fundamental modes of alpha-Bi2O3 and leads to a force field wh ich can be transferred to other systems containing Bi and O atoms.