Boron-substitution and defects in B2-type AlNi compound: Site-preference and influence on structural, thermodynamic and electronic properties

Abstract

Using a combination of theoretical (first-principles total-energy and electronic structure calculations) as well as experimental (structural, thermodynamics) techniques, we systematically investigated the influence of B incorporation on the structural, electronic and thermodynamic properties of a series of technologically-important B-containing AlNi matrix. Special attention was paid to calculating the energy cost of placing B at various sites within the cubic unit cell. The most energetically favorable defects were identified to be, depending on initial stoichiometry, substitutional B at Al site (BAl), Ni vacancy (VNi), or Ni antisite (NiAl). We show that the induced variation in the lattice parameters can be correlated with the type and concentration of the involved defects: e.g. the surge of VNi defects leads to a stronger lattice-parameter reduction, that of NiAl ones to a relatively weaker reduction while that of BAl defects to a much weaker influence. Both electronic band structure calculations as well as thermodynamics measurements indicate that the 3d bands of Ni are fully occupied and magnetically unpolarized and that the resulting N(EF) is very small: all studied compounds are normal conductors with no trace of superconductivity or magnetic polarization.