## Abstract

We introduce a method for treating electronic correlation in which a correlation factor is optimized using Hylleraas variational perturbation theory. The factor is defined by a number of parameters which grows only linearly with system size. We test the theory on two-electron atoms using the shielded-nucleus Hamiltonian at zeroth order, obtaining - 2.9035 a.u. for helium. The convergence of the method is investigated, and energies and intracule densities are compared with accurate variational results. The application of the theory to an N-electron problem with a Hartree-Fock Hamiltonian at zeroth order is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

Original language | English |
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Pages (from-to) | 561-567 |

Number of pages | 7 |

Journal | Chemical Physics Letters |

Volume | 310 |

Issue number | 5-6 |

Publication status | Published - 10 Sept 1999 |

## Keywords

- ATOMS
- PLESSET MP2-R12 CALCULATIONS
- TERMS
- CORRELATION CUSP
- WAVE-FUNCTIONS
- CARE
- COUPLED-CLUSTER