Electronic structure of fluorescent lamp cathode surfaces: BaO/W(001)

Abstract

The BaO/W interaction is responsible for the emission properties of barium–oxide coated tungsten electrode coils in fluorescent lamps. The electronic structure of the BaO/W(001) interface is investigated by first-principles calculations within the local-density approximation of the density functional theory using the full-potential linearized augmented plane wave method. Results are presented for the total density of states (DOS), the atom- and orbital-resolved partial DOS and charge density distributions. Partial covalent character in the W–O and W–Ba bonding is shown. The main contribution to chemical bonding is caused by the tungsten d states and the adsorbate valence states, which interestingly also involve barium d states. This leads to a stabilization of the adsorbed configuration, with respect to cathode operation temperatures. The calculated work function is in agreement with experimental data.