Theoretical Study on Thermodynamic Hydrogen Isotope Effect of VQ2 (Q=H, D and T)

Abstract

Abstract Based on ab-initio principle and pseudo-potential plain wave function combined with density function theory, crystal lattice dynamical characteristics and thermodynamical functions of V, VH 2 , VD 2 and VT 2 were calculated. The thermodynamical isotope effect was analyzed based on those calculated data. Calculation results show that both difference of vibration frequency of atoms in V Q 2 ( Q =H, D and T) and difference of oscillation frequency of hydrogen isotopes are mainly responsible for the hydrogen isotope effect. The standard Gibbs free energy change of the absorption reaction rises from −50 kJ/mol to 140 kJ/mol with the temperature increasing from 10 K to 1000 K. The equilibrium pressure climbs drastically when temperature is higher than room temperature. Within the whole temperature range, only inverse hydrogen isotope effect is found