Local density of states in amorphous Ni-P alloys

Abstract

The electronic density of states around the P and Ni atoms in amorphous alloys NixP1-x for different x(0.08<x<0.26) is investigated using X-ray emission. The Ni d band of the alloy is shifted to higher binding energies by 0.2 eV with respect to that of the pure Ni. The P 3s band becomes more localized and strongly bonded at a binding energy of -13.1 eV. The P 3p band is hybridized with the Ni d band and forms bonding and antibonding bands. The antibonding p band is located at +6.4 eV above the Fermi level, whereas the bonding p band is at-5.9 eV. The d densities of states around the P atoms show special features with respect to those in pure P. These new P d states (at -2.5 eV binding energy, including 0.3 d electrons) come from Ni d states. An amount of 0.3-0.4 electrons (per P atom) is transferred from the Ni atoms to P. This charge transfer corresponds to 0.1 electron per Ni atom. The experimental results have been confirmed by two types of local density calculation using either a cluster approximation or an infinite periodic lattice model where a definite number of Ni atoms are substituted by P impurities. Both computational methods characterize well the measured local and partial density of states.