AB-INITIO INVESTIGATION OF THE CS IR(001) SYSTEM/

The work function of an Ir(001) surface coated with a Cs overlayer is investigated by using the jellium sphere/slab model containing three l ayers of Ir slab, and a work function versus coverage curve much close r to the experimental one is obtained. The theoretical value of the wo rk function at theta = 0.0 (clean surface) is reduced to 5.84 eV from the former result 6.6 eV, which is now in good agreement with the expe riment (5.5 eV). The minimum of the work function is found to be 1.02 eV (former value about 0.2 eV), which is also much closer to the exper imental result (about 1.3 eV). The relationship between the work funct ion and the transition of the valence electrons in the jellium sphere- vacuum region is analysed.