We perform first-principles density-functional-theory calculations to determine the stability and associated physical and electronic properties of different adsorption phases of N on Cu ͑100͒ and Cu ͑110͒ substrates for coverages ranging from 0.125 to 1 monolayer ͑ML͒. For N on Cu ͑100͒, we consider adsorption in fourfold hollow sites while for N on Cu ͑110͒, we consider various adsorption sites including N-induced missing-row surface reconstructions and the surface nitridelike, "pseudo-͑100͒" reconstruction. We report the atomic and electronic structure and compare with analogous results for N/Cu ͑111͒. By combining results from our previous study of the N/Cu ͑111͒ system with the current investigations, we predict the possible morphology of a Cu crystal in different nitrogen environments by performing a Wulff construction at appropriate chemical potentials of nitrogen. We also find that all low-energy N/Cu surface structures-namely, Cu ͑100͒-c͑2 ϫ 2͒-N and the surface nitrides found on Cu ͑110͒ and Cu ͑111͒-share a common geometric feature: i.e., surface nanopatterns resembling 1 atomic layer of Cu 3 N ͑100͒. These nanopatterned structures exist for a narrow range of nitrogen chemical potentials before the onset of bulk Cu 3 N, unless kinetically hindered. This qualitative behavior of the predicted formation of thin-surface nitridelike structures prior to the bulk nitride material is very similar to that for transition-metal surfaces in an oxygen atmosphere, where surface oxidelike structures are predicted to be thermodynamically stable prior to bulk oxide formation.

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