Ab initio calculation of the pleochroism of fayalite

Abstract

Optical properties of fayalite, Fe 2SiO4, have been obtained from ab initio calculations on the basis of the self-consistent energy band structure. The semi-relativistic, extended linear-augmented plane wave method (ELAPW) was used. Comparison of the calculated polarized optical spectra with experimental absorbance spectra shows satisfactory agreement. This observation allows a semiquantitative interpretation of the origins of the observed d-d transitions. Energy level diagrams for Fe 21 ions in the M1 and M2 sites have been constructed using the Xa-scattered waves cluster method. These calculations quantitatively justify the use of the relationship DE ‘ 1/R 5 , which is often used for the derivation of crystal-field stabilization energies at high pressures.