AB INITIO CALCULATIONS OF BAND STRUCTURES AND DIELECTRIC FUNCTIONS OF -QUARTZ
α-quartz is one of the most critical crystalline forms of silicon dioxide; it is typically found in optical components, piezo-electric instruments, microelectronics, and geological dating. The value of bandgap and dielectric function of α-quartz is still a matter of doubt. In this study variety of first-principles calculations were performed, to calculate the electronic structure and dielectric function of α-quartz and compared those results with experimental result. GGA, HSE, and self-consistent GW approximations were used to calculate electronic structure. RPA, RPA+LFE, and BSE methods were used to calculate dielectric functions. The values of bandgap with GGA, HSE, and GW approximations are 5.74 eV, 7.51 eV, and 8.62 eV, respectively. The calculated optical gap with RPA and RPA+LFE approximations are the same at 5.7 eV, and the absorption spectra peaks are located at 10.11 eV, 12.33 eV, 14.23 eV, and 17.61 eV. The optical gap via the BSE method is 8.66 eV. In BSE calculation, only the first peak has been calculated, which is located at 10.83 eV.
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