Ab-initio calculation method for electronic structures of charged surfaces using repeated slab and density-variable charge sheets

A new repeated-slab calculation method is developed to simulate the electronic structures of charged surfaces by arranging density-variable charge sheets in vacuum regions to realize a constant potential on the charge sheets and maintain the charge neutrality condition. The charge sheets are fabricated so as to screen an electric field from charged slabs; consequently, they act like a counter electrode composed of flat perfect conductor, modeling a tip of a scanning tunneling microscope or a reference electrode in an electrochemical cell. This method has the virtues of ease of implementation into existing repeated-slab programs and low computational costs. The availability of the method is demonstrated by applying it to a charged H-2 molecule, and charged Al(111) and Si(111) surfaces.