Calculation of the field-emission current from a surface using the Bardeentransfer Hamiltonian method

We have developed a method for calculating the field-emission current from a clean or adsorbate-covered metal surface using the transfer Hamiltonian m ethod of Bardeen. The present formalism can be incorporated in accurate ato mistic electronic structure methods, and so is capable of addressing system specific band structure effects, adsorbate-induced resonances, and is amen able to accurate treatments of the exchange-correlation potential close to as well as far from the metal surface. It therefore goes beyond the convent ional Fowler Nordheim treatment of field emission from a metal surface. We illustrate the utility of our method by calculating the field-emission curr ent from a model jellium surface, using a local-density approximation excha nge-correlation potential, modified to include the correct similar to 1/4x asymptotic behavior in the vacuum region. We find that the Fowler-Nordheim behavior can be recovered in the limit of low fields; in the limit of high fields, where the details of the self-consistent effective potential in the neighborhood of the surface become important, meaningful deviations from t he Fowler-Nordheim current result.