## Abstract

We present a fast algorithm to calculate Coulomb/exchange integrals of prolate spheroidal electronic orbitals, which are the exact solutions of the single-electron, two-center Schrödinger equation for diatomic molecules. Our approach employs Neumann's expansion of the Coulomb repulsion 1/{divides}. x- y{divides}, solves the resulting integrals symbolically in closed form and subsequently performs a numeric Taylor expansion for efficiency. Thanks to the general form of the integrals, the obtained coefficients are independent of the particular wavefunctions and can thus be reused later.Key features of our algorithm include complete avoidance of numeric integration, drafting of the individual steps as fast matrix operations and high accuracy due to the exponential convergence of the expansions.Application to the diatomic molecules O_{2} and CO exemplifies the developed methods, which can be relevant for a quantitative understanding of chemical bonds in general.

Original language | English |
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Pages (from-to) | 5157-5175 |

Number of pages | 19 |

Journal | Journal of Computational Physics |

Volume | 231 |

Issue number | 15 |

DOIs | |

State | Published - 1 Jun 2012 |

## Keywords

- Coulomb integrals
- Diatomic molecules
- Laguerre expansions
- Molecular orbitals
- Prolate spheroidal coordinates
- Schrödinger equation