Table II.

Average Atomic Distance to the ESP Surface R_esp^a and Inner ChelpG Radii R_ChelpG

Element	Resp(Å)	RChelpG (Å)
H	1.69	1.5
Li	1.77
C	1.81	2.0
N	1.88	2.0
O	1.83	2.0
F	1.76
Na	1.80
Mg	1.86
Cl	1.90

^aAverage distance of the ESP surface to the closest atom R_esp. The ESP surface is defined as the volume surrounding the molecule in which the ab initio electron density ρ(r) (e/ų) satisfies 10⁻⁴ ≥ ρ(r) ≥ 10⁻⁵.