Local structure of Se in cancrinite: X-ray absorption fine structure theoretical analysis

A theoretical “ab initio” analysis of the polarized X-ray absorption spectrum of selenium in a cancrinite matrix based on a full multiple-scattering theory has been performed. Comparison of the theoretical spectra with the experimental results shows that Se atoms form dimerized chains in the channels of the cancrinite matrix with an interchain distance of about 4.8 Å. In addition the distribution of unoccupied partial s-, p- and d- electronic states of Se has been obtained. Density of states analysis provides some insight into the chemical bonding of Se in cancrinite. The results suggest that the interaction of Se atoms with the matrix is the cause of the unusually large Se–Se distance in dimers.