CCL: W:van der Waals Radius of Calcium for calculating ESP charges

 Sent to CCL by: "Adrian  Villegas" <adriano-,-eps.mcgill.ca>
 Hello everyone,
 I want to estimate the atomic charges from the electrostatic potential (ESP)
 calculated for the molecules.
 Now I know how to add/modify the values of the van der waals radii for elements
 in Gaussian 03 however, the vdw radius for the calcium atom is not listed
 in any of the major compilations of vdw radii that I have consulted.
 I definitely must specify a vdw radius for calcium since this element is located
 in the periphery of my molecule and, thus, directly influences the electrostatic
 potential.
 Any idea of where or how can I get at least a good estimation of this parameter?
 In my molecule, Calcium is bound to 4 or 5 oxygen atoms at an approximate
 distance of 2.37 Angs.
 Thanks a lot
 Adrian Villegas
 E-mail: adriano-,-eps.mcgill.ca