Halogen adsorption on transition-metal surfaces: A case study of Cl on Ta(110)

Through a series of ab initio calculations, we not only predict the atomic and electronic structure of CI on Ta(110), but also provide a quantitative basis for understanding a number of controversial questions regarding halogen adsorption on transition-metal surfaces. We demonstrate that a simple dipole layer model accurately describes the unexpected decrease in the work function upon halogen absorption, and that our proposed overlayer structure explains the one-dimensional streaking in the low-energy electron-diffraction pattern of the adsorbate-covered surface. An analysis of the electronic structure suggests that transition metals such as Ta look like simple metals from the point of view of highly electronegative adsorbates such as Cl.