First-principles insights into mechanical, optoelectronic, and thermo-physical properties of transition metal dichalcogenides ZrX2 (X = S, Se, and Te)

Transition metal dichalcogenides (TMDCs) belong to technologically important compounds. We have explored the structural, elastic, bonding, optoelectronic, and some thermo-physical properties of ZrX2 (X = S, Se, and Te) TMDCs in detail via the ab initio technique in this work. Elastic anisotropy indices, atomic bonding character, optoelectronic properties, and thermo-physical parameters, including melting temperature and minimum phonon thermal conductivity, are investigated for the first time. All the TMDCs under investigation possess significant elastic anisotropy and layered structural features. ZrX2 (X = S, Se, and Te) compounds are fairly machinable, and ZrS2 and ZrSe2 are moderately hard. ZrTe2, on the other hand, is significantly softer. Both covalent and ionic bondings contribute in the crystals. Electronic band structure calculations display semiconducting behavior for ZrS2 and ZrSe2 and metallic behavior for ZrTe2. Energy dependent optoelectronic parameters exhibit good correspondence with the underlying electronic energy density of state features. ZrX2 (X = S, Se, and Te) compounds absorb ultraviolet radiation effectively. The reflectivity spectrum, R(ω), remains over 50% in the energy range from 0 to ∼20 eV for ZrTe2. Therefore, this TMDC has a wide band and nonselective high reflectivity and can be used as an efficient reflector to reduce solar heating. The Debye temperature, melting point, and minimum phonon thermal conductivity of the compounds under study are low and show excellent correspondence with each other and also with the theoretically predicted elastic and bonding characteristics.