Effect of hydrogen atoms adsorption on the work function of the LaB6

This study employed first-principles density functional theory using CP2K and VASP software to investigate the effects of hydrogen atoms adsorption on the work function of the LaB₆ (001) surface. These results indicate that the most favorable adsorption site for hydrogen atoms is located on the top of the boron atoms in the center of the cell. As the hydrogen atom coverage density increases, the absolute value of the average adsorption energy decreases, while the surface work function gradually increases. The analysis shows that changes in the work function are strongly correlated with variations in dipole moment density, exhibiting a linear relationship. Furthermore, charge transfer induced by LaB₆ substrate deformation, the intrinsic charge carried by the hydrogen adsorbate, and the charge transfer resulting from the interaction between the hydrogen adsorbate and the LaB₆ surface substrate determine the variations in dipole moment. When the hydrogen coverage density is below 8.54 × 10^-2 $\mathrm{atoms}/{\AA }^2$, its effect on the material’s work function is relatively small, with the work function increasing from 2.14 eV to 2.47 eV. It is expected that this study can serve as a reference and theoretical basis for preliminary explorations into the application of LaB₆ in the NBI system.