On the necessity of f basis functions for bending frequencies

Publisher Website
Google Scholar
Abstract
The calculation of out‐of‐plane bending vibrations for π‐bonded systems appears to be extraordinarily sensitive to the choice of a one‐particle basis set. Ab initio predictions are reported for acetylene, an extreme example, at the self‐consistent field (SCF), singles and doubles configuration interaction (CISD), nth order Mo/ller–Plesset perturbation theory (MPn,n=2–4), coupled‐pair functional (CPF), and singles and doubles coupled cluster (CCSD) levels of theory. It is found that the addition of a set of f basis functions to the carbon atom changes the value of the SCF πg frequency by +45 cm−1, and the value of all correlated πg frequencies by more than +100 cm−1. Evidence is presented that this behavior is present in other π‐bonded systems. It is concluded that basis sets consisting of triple zeta plus two sets of polarization functions plus one set of f functions (TZ2P+f ) can predict highly accurate (∼1% average error) harmonic frequencies with the MP2, CPF, and CCSD methods, for a large number of molecules.

This publication has 76 references indexed in Scilit: