Partial charges on Fe and Gd atoms and isomer shift in MgCu 2 type compounds

Abstract

Partial charges on atoms can clarify the nature of bonding in crystalline solids. Charges cannot be measured in intermetallic solids; DFT based QTAIM technique has been used to derive Bader (δ) charges. In the present work, 183 Laves phase compounds of MgCu2 type crystal structure are investigated and the partial charges (Q) on the ions in the compounds are derived from internal radii, following the atom-pair bond method reported recently. The charge values obtained by the two methods are evaluated by studying their ability to predict the variation of 57Fe and 155 Gd Mossbauer isomer shift, as a function of the calculated charges on the Fe and Gd atoms in the compounds. Further, the basic conclusions from the APB model are confirmed by visualizing the bonding in MgCu2 type compounds using the Electron Localization Function (ELF), employing CASTEP software.