First-principles calculations of the structural, mechanical, electronic, and optical properties of BaX₂ (X=O, S, Se and Te) compounds

We used the first-principles to study the structural, mechanical, electronic, optical properties and phonon of alkali earth-metal Ba dichalcogenide BaX₂ (X = O, S, Se and Te). First, our calculated lattice constants are in good agreement with the known experimental values. Secondly, the binding and formation energies, bulk modulus, Young's modulus, Poisson's ratio, Debye temperature, sound velocity and phonon dispersion curves of BaX₂ compounds are given. Through basic physical property research, we found that the monoclinic structure of BaX₂ (C2/c) is very likely to exist. The modulation of elastic, electronic and optical properties of this system may be achievable. Furthermore, both elastic and optical properties indicate that BaX₂ is anisotropic. Finally, the electronic properties are studied by density of states and Mulliken population, indicating that all the compounds are mainly ionic properties.