Abstract
Pendry's layer-doubling method for the calculation of LEED intensities is explicitly derived as a direct, formally exact procedure for the solution of the system of linear equations describing interlayer multiple scattering in a crystal of finite depth. The method is generalised to, and a practical algorithm is presented for, the case of a surface structure consisting of a selvedge of NS inequivalent layers on a substrate having a repeat periodicity of m layers in the direction normal to the surface.