The program BAND performs many lattice summations which are in practice truncated. The two prime examples are the construction of the Bloch basis (and also the fit) and the construction of the Coulomb potential of the fit functions. The precision of the lattice summations is controlled by the SCREENING key
Parameters that influence the screening and tails of basis functions. Recognized options are
Criterion for negligibility of tails in the construction of Bloch sums. Default depends on Accuracy.
One of the parameters that define the screening of Coulomb-potentials in lattice sums. Depends by default on Accuracy, rmadel, and rcelx. One should consult the literature for more information.
Max. distance of lattice site from which tails of atomic functions will be taken into account for the bloch sums. Default depends on Accuracy.
One of the parameters that define screening of the Coulomb potentials in lattice summations. Depends by default on Accuracy, dmadel, rcelx. One should consult the literature for more information.
Real space lattice sums of slowly (or non-) convergent terms, such as the Coulomb potential, are computed by a screening technique. In previous releases, the screening was applied to all (long-range) Coulomb expressions. Starting from BAND98 screening is only applied in the periodicity directions. This key restores the original situation: screening in all directions.
