Computation of spectroscopic properties of van der Waals systems from post‐SCF ab initio potentials including the EICP alternative counterpoise technique

Abstract

The basis set superposition error (BSSE) is studied using the Counterpoise (CP) technique at SCF and post-SCF level in weakly bonded systems, with the aim of making manifest the overestimate introduced by the Boys and Bernardi method which does not facilitate a valid ab initio construction of potentials in van der Waals systems. The results show that the excess correction introduced by the CP method is to a large extent corrected using the version called the Indirect Counterpoise (ICP) method. The extension of this method to the exchange-polarization and exchange-charge transfer coupling terms provides good ab initio potentials from which quite satisfactory spectroscopic properties can be extracted.