Influence of uniaxial stresses on electronic and optical properties of β-K₂SO₄ crystal

In view of possible practical applications of transparent crystals for mechanical stress sensors, theoretical investigation of piezo(elasto)optic effect in crystals might be useful for searching for proper materials, possessing large coefficients of elasto-optic effect, and for determination of uniaxial stress directions of maximum piezo-optical sensitivity. The influence of the uniaxial stresses on the electronic band structure, density of states, and optical properties of potassium sulphate crystal β-K₂SO₄ have been studied in the framework of the density functional theory using the ab initio CASTEP code. Increase in the band gap, E_g of the crystal takes place for three crystallographic directions and for moderate uniaxial stresses, σ < 1.5 GPa. Dependencies of principal refractive indices and polarizabilities upon principal uniaxial stresses are discussed together with other features of electronic structure of the crystal.