### Abstract

The acceleration of ab initio electronic structure calculations has been one of the most important themes in the field of quantum chemistry since the mid-1980s when a series of single-reference theories starting from the Hartree-Fock (HF) method were already mature. The standard single-reference quantum chemical calculations consist of three time-consuming steps, namely, the Fock-matrix construction, its diagonalization to obtain the molecular orbitals (MOs) and/or one-electron density matrix, and the post-HF correlation calculation that does not appear in the HF and Kohn-Sham (KS) density functional theory (DFT) calculations. This chapter reviews the linear-scaling quantum chemical calculation for the extension to open-shell and excited-state theories based on the divide-and-conquer (DC) method. Finally, it describes the efficiencies of the DC-UHF and UMP2 methods in measuring the central processing unit (CPU) time. The performance of the present DC-CIS, DC-TDDFT, and DC-SACCI methods is numerically assessed by comparing the results with those of conventional CIS, TDDFT, and SACCI calculations.

Original language | English |
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Title of host publication | Fragmentation |

Subtitle of host publication | Toward Accurate Calculations on Complex Molecular Systems |

Publisher | wiley |

Pages | 297-321 |

Number of pages | 25 |

ISBN (Electronic) | 9781119129271 |

ISBN (Print) | 9781119129240 |

DOIs | |

Publication status | Published - 2017 Jun 21 |

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### Keywords

- DC-UHF method
- Density functional theory
- Excited-state theory
- Hartree-Fock method
- Linear-scaling divide-and-conquer quantum chemical method
- Molecular orbitals
- Open-shell systems
- Quantum chemistry
- UMP2 method

### ASJC Scopus subject areas

- Chemistry(all)

### Cite this

*Fragmentation: Toward Accurate Calculations on Complex Molecular Systems*(pp. 297-321). wiley. https://doi.org/10.1002/9781119129271.ch10