PNNL

Abstract

Structures of several lithium silicate crystals were fully optimized by minimizing the total energy with respect to atom position and lattice parameters using density functional theory (DFT) calculations within the generalized gradient approximation (GGA). Electronic density of states and atomic charges were calculated on the optimized structures. The relative stability of two forms of lithium disilicate determined from density functional theory calculations agree well with experimental results. Partial electronic density of states of different elements and crystallographical sites were determined. The results show bridging and non-bridging oxygen (oxygen ions that bond to two or one silicon ions, respectively) have distinguishable contributions to the oxygen 2s and upper valence bands. Hirshfeld and Bader population analysis were performed to obtain atomic charges of the crystals. Combining the understanding of the silicate crystal chemistry, we found that the Hirshfeld method correctly predicts relative charges of bridging and non-bridging oxygen ions thus provide additional evidence that the Hirshfeld charges better represent the bond ionicity of the silicon-oxygen bonds.