Contribution of molecular dynamics simulations and ab initiocalculations to the interpretation of Mg K-edge experimental XANES inK2O–MgO–3SiO2 glass

Abstract

The structural environment of Mg in a K-bearing silicate glass of compositionK2MgSi3O8 is investigated by x-ray absorption near-edge structure (XANES) spectroscopy at the MgK-edge. XANES calculations are performed using a plane-wave electronic structure code,and a structural model obtained by classical molecular dynamics coupled to ab initiorelaxation. Bond valence theory is used to validate plausible environments within thestructural models. Comparison between the experimental and calculated spectra enables usto conclude that the Mg atoms are located in distorted tetrahedral sites. Sitedistortions are found to be correlated to the theoretical shift of the XANES edgeposition.