Photoemission and electronic structure of tungsten-based metallic glasses and alloys.

Abstract

The structure and electronic density of states of intertransition-metal glasses of the form ${\mathit{T}}_{\mathit{x}}$${\mathrm{W}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ have been investigated, where T=Cu, Ni, and Co. The film samples were prepared by cosputtering in a chamber with a rapidly rotating, water-cooled substrate. Experiments included x-ray diffraction and ultraviolet photoemission at photon energies of 21.2 and 40.8 eV, and electronic-structure calculations were performed with a self-consistent linear combination of muffin-tin-orbitals method. For the calculations the structures were simulated by either disordered crystalline or amorphous clusters of 60--64 atoms in a periodically extended supercell. The range of amorphous alloy formation was determined approximately for each alloy series, and it was found that this range was larger when the atomic-radii difference of the two elements is larger. In both the photoemission and theoretical results for the crystalline and amorphous Cu-W alloys the Cu 3d band is a distinct feature whose position is well reproduced by the calculations. In the Ni-W and Co-W alloys the 3d and 5d bands overlap significantly. In the case of crystalline Ni-W alloys, the theory gives a good representation of the observed occupied density of states.