### Abstract

We introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree-Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals of the one-particle density matrix.

Original language | English (US) |
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Pages (from-to) | 12913-12918 |

Number of pages | 6 |

Journal | Proceedings of the National Academy of Sciences of the United States of America |

Volume | 113 |

Issue number | 46 |

DOIs | |

State | Published - Nov 15 2016 |

### All Science Journal Classification (ASJC) codes

- General

### Keywords

- Correlation
- Density matrix
- Electronic structure

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## Cite this

*Proceedings of the National Academy of Sciences of the United States of America*,

*113*(46), 12913-12918. https://doi.org/10.1073/pnas.1615729113