double OEGetPaulingVdWRadius(unsigned int elemno)
Return the Van der Waals radius for a particular atomic number as
tabulated in Linus Pauling, ``The Nature of the Chemical Bond'', 3rd
Edition, 1960. There are several experimental values for Van der Waals
radii (see also OEGetBondiVdWRadii
) and many additional values
used in molecular mechanics forcefields (including united-atom VdW radii),
so there is often no definitive notion of Van der Waals radius.