We have carried out first-principles calculations for the liquid structures of GaNa alloys containing one N atom to investigate the atomistic mechanism of the Na flux method, especially the origin of the enhanced solubility in GaNa alloys compared to pure Ga or Na metals. The local structure around a N atom deviates between the investigated liquids, pure Ga, Ga(0.8)Na(0.)2, Ga0.2Na0.8 and pure Na. Simultaneously, the calculated N solubility reproduces the experimental results qualitatively. We speculate that Ga-Ga interaction takes precedence over N-Ga one and only when a Ga fraction is small in GaNa liquid, N atoms can make bonds with Ga atoms. (C) 2006 Elsevier B.V. All rights reserved.