Steric hindrance has been regarded as a result of nonbonding atomic re
pulsion and measured in terms of empirically obtained van der Waals ra
dii. The authors sought the cause of steric hindrance using the partia
l derivatives of the energy-components with respect to a nuclear coord
inate. The results show that electrostatic interactions do not produce
steric hindrance but the restriction on electron-movement does. Namel
y, the kinetic energy pressure is the first cause of steric hindrance.
(C) 1994 John Wiley & Sons, Inc