Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies

doi:10.1063/1.2244559

Title: Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies

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Abstract

Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (c.f., thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory (DFT) and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a non-geometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as constraining the orbitals to be orthogonal.

Authors:

; Harrison, Robert J. ^[1]; Yanai, Takeshi ^[1]

ORNL

Publication Date:: Fri Sep 01 00:00:00 EDT 2006

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 978169

DOE Contract Number:: AC05-00OR22725

Resource Type:: Journal Article

Resource Relation:: Journal Name: The Journal of Chemical Physics; Journal Volume: 125; Journal Issue: 7

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; CHEMICAL BONDS; EXCITATION; FUNCTIONALS; IONIZATION POTENTIAL; THERMODYNAMICS

Citation Formats


                    Beste, Ariana, Harrison, Robert J., and Yanai, Takeshi. Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies.  United States: N. p., 2006. 
        Web.  doi:10.1063/1.2244559.

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                    Beste, Ariana, Harrison, Robert J., & Yanai, Takeshi. Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies.  United States.  doi:10.1063/1.2244559.

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                    Beste, Ariana, Harrison, Robert J., and Yanai, Takeshi. Fri .  
        "Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies".  United States.  
        doi:10.1063/1.2244559.

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@article{osti_978169,

  title        = {Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies},

  author       = {Beste, Ariana and Harrison, Robert J. and Yanai, Takeshi},

  abstractNote = {Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (c.f., thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory (DFT) and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a non-geometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as constraining the orbitals to be orthogonal.},

  doi          = {10.1063/1.2244559},

  journal      = {The Journal of Chemical Physics},

  number       = 7,

  volume       = 125,

  place        = {United States},

  year         = {Fri Sep 01 00:00:00 EDT 2006},

  month        = {Fri Sep 01 00:00:00 EDT 2006}

}

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DOI: 10.1063/1.2244559

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