As mentioned in Section 2.2, a kinematic, that is, single-scattering, theory of LEED cannot describe experimental intensities with an accuracy that is sufficient to determine atomic positions and other non-structural information about surfaces. This degree of accuracy requires the inclusion of multiple scattering at a level of sophistication that is similar to that of electronic band structure calculations; in fact, some early versions of LEED theory employed methods of 3-D band structure theory, such as Bloch waves and pseudopotentials. However, the goal of surface structure determination by iterative optimisation of atomic positions with lower-dimensional periodicity and sometimes large 2-D unit cells requires very efficient calculational schemes of the multiple scattering of electrons.