First principles calculation to investigate the structural, electronic, elastic, mechanical, and optical properties of K2NiP2 ternary compound

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.