Consistent van der Waals Radii
	Atomic radii are not precisely defined but are nevertheless widely used parameters in modeling and understanding molecular structure and interactions. The van der Waals radii determined by Bondi from molecular crystals and data for gases are the most widely used values, but Bondi recommended radius values for only 28 of the 44 main-group elements in the periodic table. In work carried out by postdoctoral research associates Manjeera Mantina and Rosendo Valero, graduate student Adam Chamberlin, and Professors Christopher Cramer and Donald Truhlar, atomic radii for the other 16 were presented; these new radii were determined from electronic structure calculations on selected van der Waals molecules in a way designed to be compatible with Bondi’s scale. The method chosen is a set of two-parameter correlations of Bondi’s radii with repulsive-wall distances calculated by relativistic coupled-cluster electronic structure calculations. The newly determined radii (in Å) are Be, 1.53; B, 1.92; Al, 1.84; Ca, 2.31; Ge, 2.11; Rb, 3.03; Sr, 2.49; Sb, 2.06; Cs, 3.43; Ba, 2.68; Bi, 2.07; Po, 1.97; At, 2.02; Rn, 2.20; Fr, 3.48; and Ra, 2.83.  Bondi also determined van der Waals radii for several transition metals and one actinide; if we combine his radii for these elements with the 44 main-group radii, we have a consistent set of radii for 54 elements.
A science & technology concentrated news item describing this work was written by Elizabeth Wilson and appears in the May 11, 2009 issue of Chemical & Engineering News.
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