Work function of polarized boron 2D atomic crystal

We discuss the method to calculate the work function of polarized materials with first principles calculation. Then we take boron 2D atomic crystal as an example. We found that the Alkali metal adsorbates decrease the work function of the surface with adsorbates, while the work function of the other surface is unaffected, when the alkali metal atoms are absorbed on only one surface of the boron sheet. The reason is attributed to the polarization between the alkali metal atoms and the boron sheet.