### Abstract

Shifting the pole of the energy denominators from the real axis to the imaginary results in a damping of the equation in degenerate cases. The term-by-term absolute value of the expression provides a simple and useful formula to treat quasidegenerate problems. The power of the new expression is illustrated on several examples calculating the correlation energy of some molecules. The Møller-Plesset results are scarcely affected by the proposed modification in normal cases but significant improvement is observed in quasidegenerate situations. The proposed formula is size consistent and its evaluation does not need extra computational effort.

Original language | English |
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Pages (from-to) | 3320-3324 |

Number of pages | 5 |

Journal | The Journal of Chemical Physics |

Volume | 104 |

Issue number | 9 |

Publication status | Published - 1996 |

### Fingerprint

### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

*The Journal of Chemical Physics*,

*104*(9), 3320-3324.

**Damping of perturbation corrections in quasidegenerate situations.** / Surján, P.; Szabados, A.

Research output: Contribution to journal › Article

*The Journal of Chemical Physics*, vol. 104, no. 9, pp. 3320-3324.

}

TY - JOUR

T1 - Damping of perturbation corrections in quasidegenerate situations

AU - Surján, P.

AU - Szabados, A.

PY - 1996

Y1 - 1996

N2 - Shifting the pole of the energy denominators from the real axis to the imaginary results in a damping of the equation in degenerate cases. The term-by-term absolute value of the expression provides a simple and useful formula to treat quasidegenerate problems. The power of the new expression is illustrated on several examples calculating the correlation energy of some molecules. The Møller-Plesset results are scarcely affected by the proposed modification in normal cases but significant improvement is observed in quasidegenerate situations. The proposed formula is size consistent and its evaluation does not need extra computational effort.

AB - Shifting the pole of the energy denominators from the real axis to the imaginary results in a damping of the equation in degenerate cases. The term-by-term absolute value of the expression provides a simple and useful formula to treat quasidegenerate problems. The power of the new expression is illustrated on several examples calculating the correlation energy of some molecules. The Møller-Plesset results are scarcely affected by the proposed modification in normal cases but significant improvement is observed in quasidegenerate situations. The proposed formula is size consistent and its evaluation does not need extra computational effort.

UR - http://www.scopus.com/inward/record.url?scp=0001660542&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001660542&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001660542

VL - 104

SP - 3320

EP - 3324

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 9

ER -