Density functional calculation of work function using charged slab systems

To check the relevance of charged-slab calculation, work functions of Al(111), Si(111) and TiO₂(110) surfaces are calculated using repeated charged slabs in density functional theory. It is shown that the charged-slab calculation can provide work functions which are in agreement with those by the conventional density-functional method using neutral surfaces. Moreover, it is shown that the charged-slab calculation is sensitive to the boundary condition; the charged surfaces often induces a non-uniform electricfield in a vacuum region, which produces unphysical interactions between repeated charged slabs and errors in calculated results unless the vacuum thickness is enough large.