A Consistent Approach toward Atomic Radii

Abstract

Hybrid-density functional calculations on methyl group substituted elemental hydrides of the form H3C−EHn (E is any main block or d block transition element and n is 0, 1, 2, 3, or 4 depending on the position of E in the periodic table) give atomic radii (RA) as the C−E bond distance minus half of the C−C bond distance of ethane. RA values show good linear correlations with the experimental covalent radii, Slater's empirical set of atomic radii, and experimental carbon-based atomic radii particularly for the main block elements. Except a few cases, the sum of any two RA values reproduces very well the corresponding mean single bond distances in molecules. Further, RA values provide the calculation of an expected density (Ds‘) of the element, which shows a good linear correlation with solid-state density of elements (Ds) when they are metals, suggesting similarity in their atomic packing. The percentage of free space (Vfree) in the solid-state calculated using Ds‘ and Ds suggests that all the metals have Vfree below 66, all the metalloids have Vfree between 66 and 71, and all the nonmetals have Vfree above 71.