JAMP  Vol.6 No.6 , June 2018
Extended Koopmans’ Approximation for CASDFT Exchange-Correlation Functional
A new density functional theory approach based on a complete active space self-consistent field (CASSCF) reference function in Extended Koopmans’ approximation is discussed. Recently, the number of generalizations of density functional theory based on a multiconfigurational CASSCF reference function with exact exchange (CASDFT) was introduced. It was shown by one of the authors (Dr. Gusarov) that such a theory could be formulated by introducing a special form of exchange-correlation potential. To take into account an active space and to avoid double counting of correlation energy the dependence from on-top pair density P2(r) as a new variable was introduced. Unfortunately, this requires a deep review and reparametrization of existing functional expressions which lead to additional computational difficulties. The presented approach does not require introducing additional variables (like on-top pair density, P2(r)) and is based on Extended Koopmans’ theorem (EKT) approximation for multiconfigurational wave function within CASSCF method.
Cite this paper: Gusarov, S. and Dmitriev, Y. (2018) Extended Koopmans’ Approximation for CASDFT Exchange-Correlation Functional. Journal of Applied Mathematics and Physics, 6, 1242-1246. doi: 10.4236/jamp.2018.66104.

[1]   Kohn, W. and Sham, L.J. (1965) Self-Consistent Equations Including Exchange and Correlation Effects. Physical Review, 140, A1133-A1138.

[2]   Hohenberg, P. and Kohn, W. (1964) Inhomogeneous Electron Gas. Physical Review, 136, B864-B871.

[3]   Colle, R. and Salvetti, O. (1990) Generalization of the Colle-Salvetti Correlation Energy Method to a Many-Determinant Wave Function. Journal of Chemical Physics, 93, 534-544.

[4]   Miehlich, B., Stoll, H. and Savin, A. (1997) A Correlation-Energy Density Functional for Multideterminantal Wavefunctions. Molecular Physics, 91, 527-536.

[5]   Grafenstein, J. and Cremer, D. (2000) The Combination of Density Functional Theory with Multi-Configuration Methods—CAS-DFT. Chemical Physics Letters, 316, 569-577.

[6]   Pollet, R., Savin, A., Leininger, T. and Stoll, H. (2002) Combining Multideterminantal Wave Functions with Density Functionals to Handle Near-Degeneracy in Atoms and Molecules. Journal of Chemical Physics, 116, 1250-1258.

[7]   Gusarov, S., Malmquist, P.-A. and Lindh, R. (2004) Using On-Top Pair Density for Construction of Correlation Functionals for Multideterminant Wave Functions. Molecular Physics, 102, 2207-2216.

[8]   Manni, G., Carlson, R., Luo, S., Ma, D., Olsen, J., Truhlar, D. and Gagliardi, L. (2014) Multiconfiguration Pair-Density Functional Theory. Journal of Chemical Theory and Computation, 10, 3669-3680.

[9]   Gusarov, S., Malmquist, P.A., Lindh, R. and Roos, B.O. (2004) Correlation Potentials for a Multiconfigurational-Based Density Functional Theory with Exact Exchange. Theoretical Chemistry Accounts, 112, 84-94.

[10]   Boada, L., Karasiov, V. and Labzowsky, L. (1991) Second-Order Correlation Potential in the Kohn-Sham Approximation for Atoms. International Journal of Quantum Chemistry, 40, 421-428.

[11]   Gusarov, S., Dmitriev, Yu., Stoyanov, S. and Kovalenko, A. (2013) Koopmans’ Multiconfigurational Self-Consistent Field (MCSCF) Fukui Functions and MCSCF Perturbation Theory. Canadian Journal of Chemistry, 91, 886-893.

[12]   Gusarov, S., Fedorova, T., Dmitriev, Yu. and Kovalenko, A. (2009) On Variational Estimates for Exchange-Correlation Interaction Obtained within Super-CI Approach to MCSCF Approximation. International Journal of Quantum Chemistry, 109, 1672-1675.

[13]   Gusarov, S., Goidenko, I., Dmitriev, Yu. and Labzowsky, L. (2007) Variational Estimates for Exchange-Correlation Interaction Obtained within Super-CI Approach to MCSCF Approximation. International Journal of Quantum Chemistry, 107, 1672-1675.

[14]   Fedorova, T., Dmitriev, Yu. and Gusarov, S. (2007) Post-Hartree-Fock Methods and Dynamic Correlation in Atoms and Molecules. Optics and Spectroscopy, 103, 717-722.