The energetic and structural properties of bcc NiCu, FeCu alloys: a   first-principles study
  Using special quasirandom structures (SQS's), we perform first-principles calculations studying the metastable bcc NiCu and FeCu alloys which occur in Fe-Cu-Ni alloy steels as precipitated second phase. The mixing enthalpies, density of state, and equilibrium lattice parameters of these alloys are reported. The results show that quasi-chemical approach and vegard rule can well predict the energetic and structural properties of FeCu alloys but fail to yield that of NiCu. The reason rests with the difference of bond energy variation with composition between NiCu and FeCu alloys induced by competition between ferromagnetic and paramagnetic state. Furthermore, the calculated results show that the energetic and structural properties of these alloys can well explain the local composition of the corresponding precipitates in ferrite steels. 
Yao-Ping Xie, Shi-Jin Zhao
cond-mat.mtrl-sci