### Abstract

An eclectic combination of cluster, perturbation, and linear expansions often provides the most compact mathematical descriptions of molecular electronic wave functions. A general theory is introduced to define a hierarchy of systematic electron-correlation approximations that use two or three of these expansion types. It encompasses coupled-cluster and equation-of-motion coupled-cluster methods and generates various perturbation corrections thereto, which, in some instances, reduce to the standard many-body perturbation methods. Some of these methods are also equipped with the ability to use basis functions of interelectronic distances via the so-called R12 and F12 schemes. Two computer algebraic techniques are devised to dramatically expedite implementation, verification, and validation of these complex electron-correlation methods. Numerical assessments support the unmatched utility of the proposed approximations for a range of molecular problems.

Original language | English (US) |
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Title of host publication | Challenges and Advances in Computational Chemistry and Physics |

Publisher | Springer |

Pages | 191-217 |

Number of pages | 27 |

DOIs | |

State | Published - Jan 1 2010 |

### Publication series

Name | Challenges and Advances in Computational Chemistry and Physics |
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Volume | 11 |

ISSN (Print) | 2542-4491 |

ISSN (Electronic) | 2542-4483 |

### Keywords

- Automated derivation and implementation
- Coupled cluster
- Equation-of-motion coupled cluster
- Explicitly correlated
- Perturbation corrections

### ASJC Scopus subject areas

- Computer Science Applications
- Chemistry (miscellaneous)
- Physics and Astronomy (miscellaneous)

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## Cite this

*Challenges and Advances in Computational Chemistry and Physics*(pp. 191-217). (Challenges and Advances in Computational Chemistry and Physics; Vol. 11). Springer. https://doi.org/10.1007/978-90-481-2885-3_8