### Abstract

We study the correlation energy in the H_{2} molecule as a function of bond distance and the electron coupling parameter that modifies the strength of electron-electron repulsion. For the unscaled electron repulsion we find an unusual complexity of the correlation energy dependence on the bond distance. This complexity remains if the electron repulsion is scaled down. We pay particular attention to the range of bond distances near the H_{2} equilibrium geometry. We confirm that good performance of the modern exchange-correlation functionals in molecular geometry optimization is due to the cancellation of errors between the exchange and correlation components. These components have different functional dependence on the electron coupling parameter, so the cancellation of errors no longer occurs when the electron repulsion is scaled down. This observation is important if the adiabatic connection theorem is used to construct the exchange-correlation functionals. It is also relevant for the performance of exchange-correlation functionals to study ionic interactions. The performance of the correlation operator in the molecular environment is also investigated and discussed.

Original language | English |
---|---|

Pages (from-to) | 4014-4019 |

Number of pages | 6 |

Journal | Journal of Chemical Physics |

Volume | 112 |

Issue number | 9 |

Publication status | Published - Mar 1 2000 |

### Fingerprint

### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

*Journal of Chemical Physics*,

*112*(9), 4014-4019.

**Electron correlation in chemical bonds.** / Rassolov, Vitaly A.; Ratner, Mark A; Pople, John A.

Research output: Contribution to journal › Article

*Journal of Chemical Physics*, vol. 112, no. 9, pp. 4014-4019.

}

TY - JOUR

T1 - Electron correlation in chemical bonds

AU - Rassolov, Vitaly A.

AU - Ratner, Mark A

AU - Pople, John A.

PY - 2000/3/1

Y1 - 2000/3/1

N2 - We study the correlation energy in the H2 molecule as a function of bond distance and the electron coupling parameter that modifies the strength of electron-electron repulsion. For the unscaled electron repulsion we find an unusual complexity of the correlation energy dependence on the bond distance. This complexity remains if the electron repulsion is scaled down. We pay particular attention to the range of bond distances near the H2 equilibrium geometry. We confirm that good performance of the modern exchange-correlation functionals in molecular geometry optimization is due to the cancellation of errors between the exchange and correlation components. These components have different functional dependence on the electron coupling parameter, so the cancellation of errors no longer occurs when the electron repulsion is scaled down. This observation is important if the adiabatic connection theorem is used to construct the exchange-correlation functionals. It is also relevant for the performance of exchange-correlation functionals to study ionic interactions. The performance of the correlation operator in the molecular environment is also investigated and discussed.

AB - We study the correlation energy in the H2 molecule as a function of bond distance and the electron coupling parameter that modifies the strength of electron-electron repulsion. For the unscaled electron repulsion we find an unusual complexity of the correlation energy dependence on the bond distance. This complexity remains if the electron repulsion is scaled down. We pay particular attention to the range of bond distances near the H2 equilibrium geometry. We confirm that good performance of the modern exchange-correlation functionals in molecular geometry optimization is due to the cancellation of errors between the exchange and correlation components. These components have different functional dependence on the electron coupling parameter, so the cancellation of errors no longer occurs when the electron repulsion is scaled down. This observation is important if the adiabatic connection theorem is used to construct the exchange-correlation functionals. It is also relevant for the performance of exchange-correlation functionals to study ionic interactions. The performance of the correlation operator in the molecular environment is also investigated and discussed.

UR - http://www.scopus.com/inward/record.url?scp=0001250840&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001250840&partnerID=8YFLogxK

M3 - Article

VL - 112

SP - 4014

EP - 4019

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 9

ER -