If effective core potentials (ECP's) are used in the monomer calculations,
it is important to add the (HF) term to the SAPT interaction
energy (see K. Patkowski, K. Szalewicz, J. Chem. Phys. 127
(2007) 164103). For examples for the calculation of (HF)
see sections 37.4 and 37.7.
37.6 SAPT with ECP's