The London--Eyring--Polanyi--Sato Formalism Applied to H sub 2 + Fe(001) Interactions

One approach to describing metal--H interactions is through an adaptation of the London--Eyring--Polanyi--Sato (LEPS) formulation of semiempirical quantum chemistry, as has been done to describe interactions of hydrogen molecules, in the gaseous phase, with metal surfaces. For example, Wolken has shown that the LEPS formalism yielded predictions, relative to H sub 2 adsorption on an Fe(001) surface, that were in agreement with experiment, whereas pairwise additive Fe--H potentials did not. It was later suggested by Markworth and Wolken that the LEPS method might also be applicable to atomistic simulations of effects of H on mechanical properties of metals. As pointed out by Markworth and Wolken, there are several advantages associated with use of the LEPS formalism: (a) it reduces the correct (i.e. the assumed) pair-potential formalism at large interatomic separations; (b) it is expressible in analytic form, which is advantageous for use in atomistic simulation models; (c) adjustment of certain input parameters allows for the modeling of a variety of potential functions. 12 ref.--AA