Assessment of CCSD(T)-F12 Approximations and Basis Sets for Harmonic Vibrational Frequencies

摘要

We consider basis set convergence and the effect of various approximations to CCSD(T)-F12 for a representative sample of harmonic frequencies (the HFREQ2014 set). CCSD(T~*)(F12~*)/cc-pYDZ-P12 offers a particularly favorable compromise between accuracy and computational cost: its RMSD <3 cm~(-1) from the valence CCSD(T) limit is actually less than the remaining discrepancy with the experimental value at the valence CCSD(T) limit (about S cm~(-1) RMSD). CCSD(T)-F12a and CCSD(T)-F12b appear to benefit from error compensation between CCSD and (T).