Among the many possible definitions for the vdW radius, the one derived from the dipole polarizability in Eq. 4 stands out for several reasons. First, it is systemindependent, opposite to statistically derived radii from molecular systems with intrinsic variations due to different chemical environments. Second, the numerical value of the vdW radius obtained from the polarizability also coincides with the average value obtained from all the free-atom definitions in Table . Third, this definition uniquely and unambiguously connects the vdW radiusa geometrical property -with an observable electronic property -the dipole polarizability -for all chemical elements.