Issue 36, 2014

Evaluation of composite schemes for CCSDT(Q) calculations of interaction energies of noncovalent complexes

Abstract

Recently, it has become possible to apply higher-order coupled-cluster methods to polyatomic systems including molecular noncovalent complexes. Due to the steep scaling of the complexity of these calculations, the size of the basis set becomes a critical factor and larger systems can be calculated only in small basis sets. To obtain the most accurate results, it is necessary to use composite schemes where the higher-order terms are added to a baseline calculation for which a larger basis set can be used. In this work, we have examined the accuracy of composite schemes where CCSDT(Q) correction calculated in a smaller basis set is added to CCSD(T), CCSD[T] and CCSDT calculations. As a benchmark, we have used CCSDT(Q)/aug-cc-pVTZ interaction energies calculated in a set of 18 small noncovalent complexes. We have found that the differences between the studied schemes are small and that it is safe to make the correction in a single step starting from the CCSD(T) baseline. The basis set dependence of the correction is strongly affected by the nature of the interaction. For dispersion-bound complexes, the correction calculated in a basis set as small as 6-31G**(0.25,0.15) improves the results consistently. On the other hand, description of polar complexes and especially hydrogen bonds is more difficult and the CCSDT(Q) correction has an incorrect sign until a rather large basis set is used; even the aug-cc-pVDZ result is not reliable in rare cases.

Graphical abstract: Evaluation of composite schemes for CCSDT(Q) calculations of interaction energies of noncovalent complexes

Supplementary files

Article information

Article type
Communication
Submitted
13 Jun 2014
Accepted
28 Jul 2014
First published
07 Aug 2014
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2014,16, 19115-19121

Author version available

Evaluation of composite schemes for CCSDT(Q) calculations of interaction energies of noncovalent complexes

L. Demovičová, P. Hobza and J. Řezáč, Phys. Chem. Chem. Phys., 2014, 16, 19115 DOI: 10.1039/C4CP02617A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements