Stable structures and electron density of states of W-Os alloys for dispenser cathodes

Os-W alloys form during the operation of osmium-coated tungsten dispenser cathodes due to the diffusion of tungsten into the coatings. The stable atomic arrangements of Os-W binary alloys with different W concentrations, in both the hcp lattice and bcc lattice, are obtained by combining first-principles calculations based on density functional Theory (DFT) and cluster expansion. The DFT calculations are performed using the Vienna ab initio simulation package (VASP). The density of states of the obtained stable W-Os alloys is obtained by DFT calculations and is used to discuss the electron emission properties of the corresponding Os-W alloys in a tungsten dispenser cathode.