Ented in ML-SA1 supplier Figure 1 [43]. The relaxed lattice parameters of CZGX (X = S
Ented in Figure 1 [43]. The relaxed lattice parameters of CZGX (X = S, Se) have been acquired by fitting the total power as a function from the volume of your unit cell applying Murghan’s equation of state [44]. The Figure 2 presents the fitted information of total energy to unit cell volume. Therefore, the optimization procedure results in the following equilibrium parameters (a, c) (5.28, ten.515 for CZGS and (five.58, 11.11 for CZGSe, which are consistent with other theoretical and experimental operates [45]. Table 1 compares our obtained calculations of lattice constants, band gap energy, GYKI 52466 MedChemExpress static dielectric continuous and the refraction index with some theoretical and experimental operates in the literature.Figure 1. Schematic representation of Cu2 ZnSnS4 and Cu2 ZnSnSe4 in their kesterite structure.,,,,,,,,,,,,Figure 2. Total power as a function of volume of (a) CZGS and (b) CZGSe in kesterite structure.Nanomaterials 2021, 11,5 ofTable 1. Calculated lattice constants a and c, band gap energy Eg , static dielectric continuous 0 , and refraction index n0 by DFT/PBE + (mBJ + U) approach for CZGS and CZGSe quaternary semiconductor compounds. CZGS Th a ( c ( Eg (eV) 0 naCZGSe Exp Th 5.58 11.fExp 5.59 11.04 f5.28 10.51 2.05 5.88 two.d5.26 five.35 b 10.84 c 10.64 b 0.76 c 2.14 f 6a two.fc5.27 5.34 d ten.50 c ten.51 d 1.88.23 c5.602 five.71 11.25 e 11.27 a 0.64 e 1.6 c 7.36 a 2.a1.28 7.47 two.1.17.52 g a[34]. b [35]. c [45].[46]. e [47].[27].g[25].three.two. Electronic Properties Initial, we investigated the band gap energy for both two kesterite compounds with mBJ + U calculations. Figure 3 gives an overview of your band structure a) for CZGS material and b) for CZGSe. As can be seen from this figure, the valence band maximum (VBM) as well as the conduction band minimum (CBM) are located at the point from the first Brillouin zone for both materials, which implies that the two materials possess a direct band gap. We note that the addition on the Hubbard potential leads similar behaviour in the band gap, as reported by [45]. The values from the band gap energy had been about two.05 eV and 1.26 eV for CZGS and CZGSe, respectively. These values are close to the experimental measurments reported by Reference [27]. For much more facts around the origin in the electronic band structure, the corresponding partial and total density of states are also presented in Figure three. The band inside the range from -6 to -4 eV inside the valence band is actually a hybridization involving the s-orbital of Zn and p-orbitals of S/Se and Ge; meanwhile, the bands near the Fermi level are dominated by Cu-d orbitals having a little contribution from p-orbitals of S/Se and Ge. On the other side of the band structure, the bottom in the conduction band is basically formed in the s-Ge and p-S orbitals; the rest in the conduction band is often a coupling amongst p-Ge and s-Zn orbitals. By the application of strain around the structure, the gap worth is totally modified; the band structure of both CZGS and CZGSe with unique prices of applied strain is presented in Figure four. The percentage selection of the biaxial strain was selected as among -6 and +6 by step of two , where the 0 represents the equilibrium states, as shown in Figure three plus the negative (constructive) represents compressive (tensile) strain. In all circumstances, no modifications had been observed on the nature on the band gap; whatever the intensity of the applied strain, the materials generally present a direct band gap at Gamma point. Nonetheless, the difference appears on the energy band gap value in comparison for the equilibrium state.
