Calculated lattice distortions at an isolated step on body-centered-cubic {100} surfaces

A theoretical estimate of the physically important lattice distortion around an isolated step on a crystal surface is made. The estimate makes use of our simple modified point-ion model of metal surface relaxation, but requires a computationally difficult limiting process, and use of more rapidly convergent expressions for the energy of relaxation than previously given. The procedure is general, but is illustrated by its application to [001] monatomic steps on body-centered-cubic (bcc) {100} surfaces. The isolated step was approached by calculating the lattice distortions at the steps that are found on a particular sequence of high-Miller-index surfaces, i.e., bcc {310}, {510}, {710}, {910}, and {11 1 0}, which have {100} terraces of increasing width, and extrapolating to infinite width. The results, which require a large extrapolation, indicate that the shifts of the atoms on top of the step are approximately 0.15a (with a the lattice parameter) normal to the terrace and inward, and less than 0.16a in the direction parallel to the terrace, perpendicular to the step edges, and outward. The shifts of the atoms at the bottom of the steps are almost wholly in the plane of the terrace and are estimated to be smaller than 0.16a. © 1988 The American Physical Society.