Computational insight into structural, electronic and thermal properties of novel two-dimensional NiXO (X = Cl, Br) monolayers: Ab initio perspective

The exciting developments in the study of 2D monolayers have inspired us to explore the structural, magnetic, electronic and thermal properties of novel two-dimensional monolayers of transition metal oxy-halides NiXO (X = Cl, Br) by density functional theory calculations. The structural stability and thermodynamic stability of NiXO (X = Cl, Br) monolayers are verified by binding energy calculations as well as by calculating the phonon dispersion curves. In band structure calculation, NiXO (X = Cl, Br) monolayers are metallic in nature and by applying strain (compression and elongation), these 2D monolayers shows metal–insulator transition (MIT) for up spin and metal–semiconductor transition (MST) for down spin. We also determined the tensile strength (σ) and observed that NiClO (51.86 Kbar at + 8 % strains) has more strength than NiBrO (30.30 Kbar at + 5 % strain). Magnetism also induced in these two novel monolayers and it increases with strain percentage. In thermal properties, we have investigated the specific heat, free energy and entropy of these materials and found that entropy and specific heat increases with the increase in temperature while free energy decreases with the increase in temperature. Due to its interesting properties, these novel monolayers could be a rather good candidate material for electro-thermal, spintronics, switching mechanism and memory based devices applications.