## Orbital spaces in the divide-expand-consolidate coupled cluster method

## Abstract

The theoretical foundation for solving coupled cluster singles and doubles (CCSD) amplitude equations to a desired precision in terms of independent fragment calculations using restricted local orbital spaces is reinvestigated with focus on the individual error sources. Four different error sources are identified theoretically and numerically and it is demonstrated that, for practical purposes, local orbital spaces for CCSD calculations can be identified from calculations at the MP2 level. The development establishes a solid theoretical foundation for local CCSD calculations for the independent fragments, and thus for divide–expand–consolidate coupled cluster calculations for large molecular systems with rigorous error control. Based on this theoretical foundation, we have developed an algorithm for determining the orbital spaces needed for obtaining the single fragment energies to a requested precision and numerically demonstrated the robustness and precision of this algorithm

- Authors:

- Aarhus Univ. (Denmark). qLEAP Center for Theoretical Chemistry, Dept. of Chemistry

- 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:
- 1565471

- Alternate Identifier(s):
- OSTI ID: 1421168

- Grant/Contract Number:
- AC05-00OR22725

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Chemical Physics

- Additional Journal Information:
- Journal Volume: 144; Journal Issue: 16; Journal ID: ISSN 0021-9606

- Publisher:
- American Institute of Physics (AIP)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- Chemistry; Physics

### Citation Formats

```
Ettenhuber, Patrick, Baudin, Pablo, Kjærgaard, Thomas, Jørgensen, Poul, and Kristensen, Kasper. Orbital spaces in the divide-expand-consolidate coupled cluster method. United States: N. p., 2016.
Web. doi:10.1063/1.4947019.
```

```
Ettenhuber, Patrick, Baudin, Pablo, Kjærgaard, Thomas, Jørgensen, Poul, & Kristensen, Kasper. Orbital spaces in the divide-expand-consolidate coupled cluster method. United States. doi:10.1063/1.4947019.
```

```
Ettenhuber, Patrick, Baudin, Pablo, Kjærgaard, Thomas, Jørgensen, Poul, and Kristensen, Kasper. Thu .
"Orbital spaces in the divide-expand-consolidate coupled cluster method". United States. doi:10.1063/1.4947019. https://www.osti.gov/servlets/purl/1565471.
```

```
@article{osti_1565471,
```

title = {Orbital spaces in the divide-expand-consolidate coupled cluster method},

author = {Ettenhuber, Patrick and Baudin, Pablo and Kjærgaard, Thomas and Jørgensen, Poul and Kristensen, Kasper},

abstractNote = {The theoretical foundation for solving coupled cluster singles and doubles (CCSD) amplitude equations to a desired precision in terms of independent fragment calculations using restricted local orbital spaces is reinvestigated with focus on the individual error sources. Four different error sources are identified theoretically and numerically and it is demonstrated that, for practical purposes, local orbital spaces for CCSD calculations can be identified from calculations at the MP2 level. The development establishes a solid theoretical foundation for local CCSD calculations for the independent fragments, and thus for divide–expand–consolidate coupled cluster calculations for large molecular systems with rigorous error control. Based on this theoretical foundation, we have developed an algorithm for determining the orbital spaces needed for obtaining the single fragment energies to a requested precision and numerically demonstrated the robustness and precision of this algorithm},

doi = {10.1063/1.4947019},

journal = {Journal of Chemical Physics},

number = 16,

volume = 144,

place = {United States},

year = {2016},

month = {4}

}

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