Nitrogen Dissolution in Liquid Ga and Fe: Comprehensive Analysis, Relevance for Crystallization of GaN.

The dissolution of molecular nitrogen in Ga and Fe was investigated by calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between and and states whereas for Fe this is by to , and states. Accordingly, the energy of dissolution of N2 for arbitrarily chosen starting atomic configurations was 0.535 eV/mol and -0.299 eV/mol for Ga and Fe, respectively. For configurations optimized with molecular dynamics, the difference between the corresponding energy values, 1.107 eV/mol and 0.003 eV/mol, was similarly large. Full thermodynamic analysis of chemical potential was made employing entropy-derived terms in a Debye picture. The entropy-dependent terms were obtained via a normal conditions path to avoid singularity of ideal gas entropy at zero K. Nitrogen solubility as a function of temperature and N2 pressure was evaluated, being much higher for Fe than for Ga. For T=1800 K and p=104 bar, the N concentration in Ga was 3×10-3 at. fr. whereas for Fe, it was 9×10-2 at. fr. in very good agreement with experimental data. It indicates that liquid Fe could be a prospective solvent for GaN crystallization from metallic solutions.