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For the equilibrium immiscible Cu-Co system with a positive heat of formation of +10 kJ mol −1 , ab initio calculations were used to predict the physical properties of the metastable D0 19 and L1 2 structures for the Cu 75 Co 25 phases and the D0 19 structure for the Cu 25 Co 75 alloy. Based on the ab initio calculation results, an n-body Cu-Co potential was constructed and proven to be realistic. Applying the constructed Cu-Co potential, molecular dynamics simulations predict that the amorphous phase could be obtained at around Cu 60 Co 40 and its atomic distribution could be inhomogeneous. Experimentally, by using ion beam mixing with 200 keV Xe + ions, an amorphous Cu 60 Co 40 phase with inhomogeneous morphology was indeed obtained at a dose of 1 × 10 15 Xe + cm −2 . Increasing the irradiation dose to 4 × 10 15 Xe + cm −2 , a mixture of Cu-rich and Co-rich metastable phases was obtained. Besides, a mixture of FCC and HCP structures was observed in the Cu 82 Co 18 multilayered sample and an HCP structure was observed in the Cu 26 Co 74 multilayered sample. It was found that the lattice constants of the FCC and HCP phases determined by diffraction analysis were quite compatible with those predicted by the ab initio calculations.

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