Characterization of the structural and electronic properties of crystalline lithium silicates

Density functional theory (DFT) calculations within the generalized gradient approximation (GGA) were performed to study the atomic and electronic structure of lithium silicate crystals that were fully optimized within the theory. It is found that the relative stability of two crystalline forms of lithium disilicate agrees well with experimental results. The calculated electronic density of states shows distinguishable contributions to the oxygen 2s and upper valence bands associated with bridging (BO) and nonbridging oxygen (NBO) atoms. Bond ionicity, characterized by determining the relative atomic charges, is used to distinguish BO and NBO atoms as well as the corresponding Si-BO and Si-NBO bonds. Results from this work reveal that atomic charges obtained by using population analysis methods based on electron deformation density rather than total electron density provide an accurate description of bond ionicity consistent with chemical intuition.