You should verify that the coordination chemistry built in using the OVERLAP cards is realistic. It is particularly important to specify all the nearest neighbors of a typical atom in the shell to be overlapped. The most important factor in determining the scattering amplitudes is the atomic number of the scatterer, but the coordination chemistry should be approximately correct to ensure good scattering potentials. Thus it is important to specify as accurately as possible the coordination environment of the scatterer. Note: If you use the OVERLAP card, then you cannot use the FMS or SCF cards. Also the pathfinder won't be called and you must explicitly specify single scattering paths using the SS card .
* Example 1. Simple usage * Determine approximate overlap for central and 1st nearest neighbor in Cu OVERLAP 0 determine overlap for central atom of Cu *iphovr novr rovr * ipot, number in shell, distance 1 12 2.55266 OVERLAP 1 determine approximate overlap for 1st shell atoms *iphovr novr rovr * ipot, number in shell, distance 0 12 2.55266 * Example 2. More precise usage * Determine approximate overlap for 3rd shell atoms of Cu OVERLAP 3 0 1 2.55266 ipot, number in shell, distance 1 4 2.55266 2 7 2.55266 2 6 3.61000 2 24 4.42133