Prediction of structural parameters and physical properties of CsHSO3 up to 60 GPa

Ab initio calculations based on density-functional theory have been used to predict the position of the hydrogen atom in CsHSO3 and the pressure dependence of structural parameters and physical properties up to 60 GPa. For the calculations, a generalized gradient approximation, pseudopotentials, and a constant pressure relaxation based on a Broyden-Fletcher-Goldfarb-Shanno algorithm were used. At ambient pressure all calculated structural parameters coincide within 3% with experimental data. The S-H stretch frequency calculated within a frozen-phonon approach matches experimental observations within 2%. The present calculations predict a tetrahedral HSO3- ion with a S-H distance of 1.35 Angstrom. Above 20-30 GPa a framework of HSO3- units, interconnected by trifurcated S-H ... O bonds, forms. The pressure dependence of optical properties was also predicted: for 0 (60) GPa the calculations give a double refraction of -0.046 (-0.025) and a dispersion of 0.013 (0.018). [S0163-1829(98)01107-2].