Electronic structures of amorphousNi1−xPxglasses

Abstract

Electronic structures of amorphous ${\mathrm{Ni}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{P}}_{\mathrm{x}}$ glasses for x=0.25, 0.20, and 0.15 are calculated with use of the orbital charge self-consistent orthogonalized linear combination of atomic orbitals method. Periodic structural models containing 100 atoms each are constructed first, using the Monte Carlo method. Results are presented for the total and partial density of states (DOS), joint DOS, localization index for each state, effective charges on each atom, and DOS at the Fermi level ($E_F$). The $E_F$ is located at the steep edge of the Ni d band resulting in a Ni d-band hole in all three glasses. The local DOS of Ni atoms depends very sensitively on the number of P atoms as nearest neighbors while the local DOS of P atoms is rather insensitive to the atomic environment. For Ni atoms with no P atom as a nearest neighbor, its local DOS has a sharp peak above $E_F$ and its effective charge is much reduced. Mulliken charge analysis indicates that on average, P atom gains about 0.4 to 0.8 electrons from Ni atoms for x ranges from 0.25 to 0.15. The average conduction electron per Ni atom is calculated to be 1.5 electron. The high resistivity of a-${\mathrm{Ni}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{P}}_{\mathrm{x}}$ glasses may be related to the existence of localized electron states near $E_F$.