Fit of charges due to the electrostatic potential:

$esp_fit fits point charges at the positions of nuclei to electrostatic potential arising from electric charge distribution (for UHF cases also for spin density, also possible in combination with $soghf). For this purpose the ("real") electrostatic potential is calculated at spherical shells of grid points around the atoms. By default, Bragg-Slater radii, $r_{BS}$ mathend000#, are taken as shell radii.

A parametrization very close to that suggested by Kollman (a multiple-shell model with shells of radii ranging from 1.4*$r_{vdW}$ mathend000# to 2.0*$r_{vdW}$ mathend000#, $r_{vdW}$ mathend000# is the van-der-Waals radius; U.C. Singh, P.A. Kollman, J. Comput. Chem. 5(2), 129-145 (1984)) is used if the keyword is extended:

$esp_fit kolman