Crystal structure and band gap studies of hydrogarnet calculated results by density functional theory

Abstract

Herein, we investigate the hydrogarnet sample by X-ray diffraction and calculated the related garnets included grossular, katoite and hydrogrossular by density functional theory to investigate the effect of silicon composition. The results of X-ray diffraction suggests that the chemical formula should be Ca2.93Al1.97Si0.64O2.56(OH)9.44. The optimized lattice parameters are in good agreement with the available data. We demonstrated the structural details of oxygen tetrahedron with or without silicon and found the stability and the band gap of garnet to be selectively modified by controlling the distribution and concentration of silicon atoms at different structural deformation levels. Moreover, the hydrogrossular configuration with the silicon atoms in separate manner is favored of the high stability and large band gap. It is firstly proposed that the band gap of hydrogarnet should be 3.17-3.65 eV by first-principles calculations. This was explained by the majority of the DOS contributions from the electrons in O and Ca atoms. It is believed that our research contributes to the mechanism of silicon distribution in garnet and helps the further disposal and treatment of silicate mud.