Structural stability of GaNxAs1-x including zinc blende (ZB)-wurtzite (W) structures and miscibility is systematically investigated based on a newly developed empirical potential, which incorporates electrostatic energies due to bond charges and ionic charges. Using the empirical potential, the system energies of ZB and W forms are calculated for bulk GaNxAs1-x over the entire concentration range. The calculated results predict that the structural phase transition from ZB to W occurs at xsimilar to0.4, which differs from xsimilar to0.7 estimated by electrostatic energy contributions. The shift of the ZB-W structural transition concentration toward xsimilar to0.4 is clarified in terms of difference in bond length between ZB-and W-GaNxAs1-x. Based on these findings, the miscibility of GaNxAs1-x is discussed by excess energy calculations. (C) 2003 Elsevier B.V. All rights reserved.