In this article, a theoretical analysis to measure the band composition, optical properties and density of states (DOS) of rutile titanium dioxide was conducted via the castep simulation program. Calculations of the first principles were carried out using the super cell (1x1x1) process. The first computation of concepts was studied by density functional theory (DFT) with a generalized gradient approximation from Perdew-Wang's 1991 (GGA-PW91), local density approximation (LDA) for exchange-correlation energy functional, and (LDA)+U method, implementation of coulomb interactions btween of ( ) atom and of ( ) atom.All experimental values are agreed with our results. The results for LDA and GGA-Pw91 indicated weaknesses in the estimation and far from the experimental results for the properties of the rutile under analysis, except for the energy band difference, although the estimation data (LDA) + U was in accordance with the experimental values. The optical properties of rutile was obtained using several methods of exchange correlations, well in accordance with experimental findings and other theoretical evidence.
In this article, the lattice constants, band structure and optical characteristics of ZnO wurtzite structure under various pressures were studied using the generalized gradient approximation (GGA) method. This method is based on the functional density (DFT) Theory, according to the first principle. The results show that as the pressure increases and the band gap increases, the lattice constants (a and c) decrease. As the pressure increases, the minimum conduction band will move to a higher energy level, and the maximum valence band will move to a lower energy level, thereby increasing the energy band difference. As the pressure increases, the shape of the optical parameter curve remains almost unchanged, and all peaks move to higher energies. The state density, dielectric function, reflectance and absorption coefficient are also calculated. The overview of the spectrum and optical properties is discussed, including the imaginary part of the dielectric function, reflectance and absorption coefficient of wurtzite-type ZnO under environmental conditions. The optical constants indicate that the phase of ZnO wurtzite structure is transparent. We noticed that our measurements are comparable to those observed in the literature.
We systematically studied the structure, electronic, elastic and optical properties of BiGaO3 type perovskite cubes. We also report the calculation of all properties listed in the title of GGA-PBE approximation to BiGaO3.This material has a band gap which can be considered as an indirect band gap. The maximum valence band is represented by the M point (VBM), whereas the conduction band is represented by the X point (CBM)The electronic structure of BiGaO3 shows that it has a semiconductor indirect band gap of 1.37 eV.The elastic constant was determined in equilibrium confirming its accuracy. The bulk, shear, and Young's modulus were all extracted from the data. Poisson's ratio was also found. The confirmed structural parameters were in good agreement with the previously calculated experimental data. Our research suggests that BiGaO3 is a promising piezoelectric, multiferroic, ferroelectric, and photo catalytic material.
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