First-principles calculations of the structural, electronic, elastic, mechanical, and optical properties of the K2NiP2 ternary compound using density functional theory as implemented in the quantum espresso package have been performed. The calculations have been done using the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE, PBEsol) exchange-correlation functionals and the local density approximation (LDA). The lattice parameters have been found to agree with the available experimental results. Direct bandgaps have been obtained as 0.630, 0.588, and 0.525 eV when using the GGA-PBE, GGA-PBEsol, and LDA approximations, respectively. In all three scenarios, the valence bands have been noted to be majorly formed by Ni-3d and P-2p states with little contribution from the other states, whereas the conduction bands have been observed to be mainly formed by P-2p states with a small contribution from the other states. The K2NiP2 has been found to be mechanically stable, ductile, and ionic. The optical properties showed that the compound under investigation has a high refractive index and absorption coefficients covering the ultraviolet–visible regions, thus indicating its potential for photovoltaic applications. The bandgaps obtained using LDA were smaller than those obtained using GGA. This is because LDA underestimates the bandgaps.

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Efficient materials with good optoelectronic properties are required for the good performance of photovoltaic devices. In this work, we present findings of a theoretical investigation of the structural, electronic, elastic, mechanical, and optical properties of K2CuX (X = As, Sb) ternary compounds. The computations were carried out by using the density functional theory (DFT) formalism as implemented in the quantum espresso (QE) software package. The calculated lattice constants of 19.1414 a.u (K2CuAs) and 20.0041 a.u (K2CuSb) are in agreement with the experimental results from the literature. The materials under study were found to have bandgaps of 1.050 eV (K2CuAs) and 1.129 eV (K2CuSb). The valence band was majorly formed by Cu-3d, As-2p, and Cu-4s states while the conduction band was majorly dominated by Cu-5p in K2CuAs, whereas in K2CuSb, the valence band was mainly formed by Cu-3d, Cu-4s, and Sb-3p states while the conduction band was majorly formed by Sb-3p and Cu-5p states. The investigated materials were found to be mechanically stable at zero pressure, ductile, and ionic. The optical absorption coefficient curves were found to cover the ultraviolet to visible (UV-Vis) regions, thus making K2CuAs and K2CuSb good UV-Vis absorbers hence their suitability for photovoltaic applications.

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