First-principles calculations of the electronic, optical and elastic properties of CdIn₂S₄thiospinel at ambient and elevated pressure

CdIn2S4 thiospinel was studied by means of the first principles calculations in both generalized gradient and local density approximations (GGA and LDA). The structural, electronic, optical and elastic properties were calculated in the pressure range from 0 to 10 GPa, below the pressure of phase transition for this compound. One of the main results of the paper is that the previously encountered in the literature controversy regarding the character of the CdIn2S4 band gap was resolved in favor of the indirect gap. Pressure coefficient of the band gap estimated as 0.071/0.063 eV/GPa (GGA/LDA) is in excellent agreement with the found in the literature experimental data of 0.076 or 0.069 eV/GPa. Calculated pressure dependence of the unit cell volume follows the experimental results very closely. Dependence of the interionic distances, lattice parameter and all elastic constants on pressure was calculated. Refined estimations of the Debye temperature for CdIn2S4 are given as 280 K (LDA) and 252 K (GGA). Elastic anisotropy of CdIn2S4 was visualized by plotting three-dimensional dependence of the Young modulus on a direction in the crystal lattice; it was established that the lowest Young moduli values are realized if the external stress is applied along the crystallographic axes.