### Abstract

Finite-order perturbation corrections are ambiguous since they depend on the partitioning of the Hamiltonian to a zero-order part and perturbation, and any chosen partitioning can be freely modified, e.g. by level shift projectors. To optimize low-order corrections, an approximate variational procedure is proposed to determine level shift parameters from the first-order Ansatz for the wavefunction. The resulting new partitioning scheme provides significantly better second-order results than those obtained by standard partitions like Epstein-Nesbet or Møller-Plesset. We treat the anharmonic oscillator and the atomic electron correlation energy in He, Be and Ne as numerical test cases.

Original language | English |
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Pages (from-to) | 303-309 |

Number of pages | 7 |

Journal | Chemical Physics Letters |

Volume | 308 |

Issue number | 3-4 |

Publication status | Published - Jul 23 1999 |

### Fingerprint

### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Spectroscopy
- Atomic and Molecular Physics, and Optics

### Cite this

*Chemical Physics Letters*,

*308*(3-4), 303-309.

**Optimized partitioning in Rayleigh-Schrödinger perturbation theory.** / Szabados, Á; Surján, P. R.

Research output: Contribution to journal › Article

*Chemical Physics Letters*, vol. 308, no. 3-4, pp. 303-309.

}

TY - JOUR

T1 - Optimized partitioning in Rayleigh-Schrödinger perturbation theory

AU - Szabados, Á

AU - Surján, P. R.

PY - 1999/7/23

Y1 - 1999/7/23

N2 - Finite-order perturbation corrections are ambiguous since they depend on the partitioning of the Hamiltonian to a zero-order part and perturbation, and any chosen partitioning can be freely modified, e.g. by level shift projectors. To optimize low-order corrections, an approximate variational procedure is proposed to determine level shift parameters from the first-order Ansatz for the wavefunction. The resulting new partitioning scheme provides significantly better second-order results than those obtained by standard partitions like Epstein-Nesbet or Møller-Plesset. We treat the anharmonic oscillator and the atomic electron correlation energy in He, Be and Ne as numerical test cases.

AB - Finite-order perturbation corrections are ambiguous since they depend on the partitioning of the Hamiltonian to a zero-order part and perturbation, and any chosen partitioning can be freely modified, e.g. by level shift projectors. To optimize low-order corrections, an approximate variational procedure is proposed to determine level shift parameters from the first-order Ansatz for the wavefunction. The resulting new partitioning scheme provides significantly better second-order results than those obtained by standard partitions like Epstein-Nesbet or Møller-Plesset. We treat the anharmonic oscillator and the atomic electron correlation energy in He, Be and Ne as numerical test cases.

UR - http://www.scopus.com/inward/record.url?scp=0000257285&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000257285&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000257285

VL - 308

SP - 303

EP - 309

JO - Chemical Physics Letters

JF - Chemical Physics Letters

SN - 0009-2614

IS - 3-4

ER -