Free area for translation calculated by Monte-Carlo simulation of surface migrations

It is assumed that surface mobility of alkali metals adsorbed on refractory metal surfaces is achieved by hops between adjacent adsorption sites and is constrained by intermetallic bonds with the surface as well as covalent (partly ionic) bonds and dipole interaction between adsorbed particles. A survey reduces the crystallographic considerations to two basic types. A Monte-Carlo computer simulation is then performed to obtain estimates of the free area of translation. This form of the free area function is used in the prediction of emission rates from cesiated tungsten and molybdenum, and results in improved correlation with experimental data for materials of interest in the development of thermionic diodes.