| First-principles calculation of material properties in the past few decades has made great progress in a wide range of various systems. The density functional theory (DFT) has become the most widely used method for the computational physics.Nowadays,the density functional theory (DFT) is considered as the standard method in the study of electronic,structural and macroscopic properties of solids from the first-principles in condensed matter physics.Most of the semiconductorsâ…¡-â…¢2-â…¥4 have been found to crystallize in the thiogallate structure, called defect chalcopyrite(DC), with space group 14;while some of them crystallize in the defect famatinite(DF), also known as defect stannite, with higher symmetry space group I42m. They have been widely investigated because of their potential application to optoelectronic and nonlinear optical devices.In this paper, we perform the calculation by abinit software package. First-principles density functional theory(DFT) calculations are carried out in the local density approximation (LDA) and presented for a family of compounds ZnGa2X4(X=S,Se,Te).We investigate the band structures of these materials.The two possible structures, defect chalcopyrite(DC) and defect famatinite(DF) are both calculated.We reveal that ZnGa2Te4 has an indirect band-gap, while ZnGa2SS4 and ZnGa2Se4 have direct band- gaps.The LDA band-gaps are found to be very different in the DF and DC structures,while the lattice parameters and bond-length are similar.In the next section,we investigate the bulk modulus, the pressure coefficients and obtain the metallization pressures of ZnGa1X4(X=S,Se,Te). The figures of direct band gap for ZnGa2X4(X=S,Se,Te)Eg as a function of pressure P (GPa) for DC and DF structures.Eg is more a linear function of in V than a linear function of P.At the same time, we apply William Paul empirical rule for defect chalcopyrites and defect famatinites and find that the "empirical rule "is valid for ZnGa2S4 and ZnGa2Se4.We hope that the results will contribute to the understanding of this important family of ordered-vacancy compounds. |
