Abstract:

To study the thermodynamic hydrogen isotopic effect in Mg2NiQ4 (Q=H, D, T), a calculation based on first-principles and pseudo-potential plain waves combined with density function theory to determine the phonon dispersion properties of Mg2NiQ6 (Q=H, D, T) was undertaken. Thermodynamic functions were thus obtained. The hydrogen isotope effect was investigated using thermodynamic methods during the process of hydrogen isotope absorption by Mg2Ni wherein it was converted into Mg2NiQ6. Gibbs free energies of hydrogen isotopes that were reported in literature were employed for this calculation. Results show that the hydrogen isotopic effect originates from differences in opposite atomic vibration frequencies. As the temperature increases, the isotopic effect of the Mg2NiQ6 with a CaF2 structure changes froma negative isotopic effect to a positive isotopic effect.

Key words: Mg2Ni alloy, Hydrogen, Isotopic effect, Simulation