Convergence of the Interaction Energies in Noncovalent Complexes in the Coupled-Cluster Methods Up to Full Configuration Interaction

Lucia Šimová; Jan Řezáč; Pavel Hobza

doi:10.1021/ct4002762

Convergence of the Interaction Energies in Noncovalent Complexes in the Coupled-Cluster Methods Up to Full Configuration Interaction

J Chem Theory Comput. 2013 Aug 13;9(8):3420-8. doi: 10.1021/ct4002762. Epub 2013 Jul 18.

Authors

Lucia Šimová¹, Jan Řezáč², Pavel Hobza^{1

2}

Affiliations

¹ Regional Center of Advanced Technologies and Materials, Department of Physical Chemistry, Palacký University , 771 46 Olomouc, Czech Republic.
² Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , 166 10 Prague, Czech Republic.

PMID: 26584097
DOI: 10.1021/ct4002762

Abstract

The CCSD(T) method stands out among various coupled-cluster (CC) approximations as the "golden standard" in computational chemistry and is widely and successfully used in the realm of covalent and noncovalent interactions. The CCSD(T) method provides reliable interaction energies, but their surprising accuracy is believed to arise partially from an error compensation. The convergence of the CC expansion has been investigated up to fully iterative pentuple excitations (CCSDTQP); for the smallest eight electron complexes, the full CI calculations have also been performed. We conclude that the convergence of interaction energy at noncovalent accuracy (0.01 kcal/mol) for the complexes studied is reached already at CCSDTQ or CCSDT(Q) levels. When even higher accuracy (spectroscopic accuracy of 1 cm(-1), or 3 cal/mol) is required, then the noniterative CCSDTQ(P) method could be used.