First-principles study of nickel-silicides ordered phases

We present a study of nickel-silicides ordered alloys by means of first-principles calculations. Emphasis was put on the phases (low and high temperatures) identified in the binary phase diagram, namely: Ni3Si-beta(1), -beta(2), and -beta(3), Ni31Si12-gamma, Ni2Si-delta, -theta, Ni3Si2-epsilon, NiSi-MnP and NiSi2-alpha. In addition, some common structures are computed for information: L1(2), D0(3) and D0(22). The simulations reproduce with a high accuracy lattice parameters and formation energies of main experimental structures, except for beta(2) and beta(3). Our results clarify the crystallographic nature of the gamma structure, and the comparison of experimental Raman spectra and vibrational calculations will help experimentalists to identify without ambiguity NiSi3 structures. (C) 2010 Elsevier B.V. All rights reserved.