Local lattice relaxations in random metallic alloys: Effective tetrahedron model and supercell approach

We present a simple effective tetrahedron model for local lattice relaxation effects in random metallic alloys on simple primitive lattices. A comparison with direct ab initio calculations for supercells representing random ${\mathrm{Ni}}_{0.50}{\mathrm{Pt}}_{0.50}$ and ${\mathrm{Cu}}_{0.25}{\mathrm{Au}}_{0.75}$ alloys as well as the dilute limit of Au-rich CuAu alloys shows that the model yields a quantitatively accurate description of the relaxtion energies in these systems. Finally, we discuss the bond length distribution in random alloys.