# The same number of optimized parameters scheme for determining intermolecular interaction energies

## Abstract

We introduce the Same Number Of Optimized Parameters (SNOOP) scheme as an alternative to the counterpoise method for treating basis set superposition errors in calculations of intermolecular interaction energies. The key point of the SNOOP scheme is to enforce that the number of optimized wave function parameters for the noninteracting system is the same as for the interacting system. This ensures a delicate balance between the quality of the monomer and dimer finite basis set calculations. We compare the SNOOP scheme to the uncorrected and counterpoise schemes theoretically as well as numerically. Numerical results for second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster with single, double, and approximate triple excitations (CCSD(T)) show that the SNOOP scheme in general outperforms the uncorrected and counterpoise approaches. Moreover, we iterate that SNOOP interaction energies calculated using a given basis set are of similar quality as those determined by basis set extrapolation of counterpoise-corrected results obtained at a similar computational cost.

- Authors:

- Aarhus Univ. (Denmark)

- Publication Date:

- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1565341

- Grant/Contract Number:
- AC05-00OR22725

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Chemical Physics

- Additional Journal Information:
- Journal Volume: 142; Journal Issue: 11; Journal ID: ISSN 0021-9606

- Publisher:
- American Institute of Physics (AIP)

- Country of Publication:
- United States

- Language:
- English

### Citation Formats

```
Kristensen, Kasper, Ettenhuber, Patrick, Eriksen, Janus Juul, Jensen, Frank, and Jørgensen, Poul. The same number of optimized parameters scheme for determining intermolecular interaction energies. United States: N. p., 2015.
Web. doi:10.1063/1.4915141.
```

```
Kristensen, Kasper, Ettenhuber, Patrick, Eriksen, Janus Juul, Jensen, Frank, & Jørgensen, Poul. The same number of optimized parameters scheme for determining intermolecular interaction energies. United States. doi:10.1063/1.4915141.
```

```
Kristensen, Kasper, Ettenhuber, Patrick, Eriksen, Janus Juul, Jensen, Frank, and Jørgensen, Poul. Fri .
"The same number of optimized parameters scheme for determining intermolecular interaction energies". United States. doi:10.1063/1.4915141. https://www.osti.gov/servlets/purl/1565341.
```

```
@article{osti_1565341,
```

title = {The same number of optimized parameters scheme for determining intermolecular interaction energies},

author = {Kristensen, Kasper and Ettenhuber, Patrick and Eriksen, Janus Juul and Jensen, Frank and Jørgensen, Poul},

abstractNote = {We introduce the Same Number Of Optimized Parameters (SNOOP) scheme as an alternative to the counterpoise method for treating basis set superposition errors in calculations of intermolecular interaction energies. The key point of the SNOOP scheme is to enforce that the number of optimized wave function parameters for the noninteracting system is the same as for the interacting system. This ensures a delicate balance between the quality of the monomer and dimer finite basis set calculations. We compare the SNOOP scheme to the uncorrected and counterpoise schemes theoretically as well as numerically. Numerical results for second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster with single, double, and approximate triple excitations (CCSD(T)) show that the SNOOP scheme in general outperforms the uncorrected and counterpoise approaches. Moreover, we iterate that SNOOP interaction energies calculated using a given basis set are of similar quality as those determined by basis set extrapolation of counterpoise-corrected results obtained at a similar computational cost.},

doi = {10.1063/1.4915141},

journal = {Journal of Chemical Physics},

number = 11,

volume = 142,

place = {United States},

year = {2015},

month = {3}

}

Works referenced in this record:

##
The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors

journal, October 1970

- Boys, S.F.; Bernardi, F.
- Molecular Physics, Vol. 19, Issue 4, p. 553-566