EXPLICIT PERIODIC TREND OF VANDERWAALS RADII

van der Waals radii of covalently bonded nonmetal atoms are suggested to vary in a row of the periodic table as cN/ In (cN), where N is the number of valence electrons, and in a column as ab-1/(n'-1), where n' is the Born exponent. The reliability of the analytically homogeneous set of van der Waals radii given by the empirical formula 3 is shown by comparison with reference values issued from Pauling's and Bondi's recommendations. The latter are interpolated or extrapolated by means of an extended correlation with covalent or atomic radii. The values obtained are transferable to atoms in current molecular packings resulting from an average dispersion effect: this standard compression of the atomic spheres rationalizes the discrepancy between the van der Waals radii serving to estimate the distance of closest approach between nonbonded atoms (r(w)) and the equilibrium values (r*) occurring in phenomenological van der Waals potentials of molecular mechanics force fields. A quantitative correlation between r(w) and r* is outlined.