A perturbation-based super-CI approach for the orbital optimization of a CASSCF wave function

Journal of Computational Chemistry
Christian KollmarFrank Neese

Abstract

A perturbation theory-based algorithm for the iterative orbital update in complete active space self-consistent-field (CASSCF) calculations is presented. Following Angeli et al. (J. Chem. Phys. 2002, 117, 10525), the first-order contribution of singly excited configurations to the CASSCF wave function is evaluated using the Dyall Hamiltonian for the determination of a zeroth-order Hamiltonian. These authors employ an iterative diagonalization of the first-order density matrix including the first-order correction arising from single excitations, whereas the present approach uses the single-excitation amplitudes directly for the construction of the exponential of an anti-Hermitian matrix resulting in a unitary matrix which can be used for the orbital update. At convergence, the single-excitation amplitudes vanish as a consequence of the generalized Brillouin's theorem. It is shown that this approach in combination with direct inversion of the iterative subspace (DIIS) leads to very rapid convergence of the CASSCF iteration procedure. © 2019 Wiley Periodicals, Inc.

References

Apr 25, 2006·Physical Chemistry Chemical Physics : PCCP·Florian Weigend
Jul 13, 2006·The Journal of Physical Chemistry. a·André R GroenhofKoop Lammertsma
Jun 15, 2007·Journal of Computational Chemistry·Florian Weigend
May 2, 2009·The Journal of Chemical Physics·Florian WeigendReinhart Ahlrichs

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Citations

Aug 21, 2020·Physical Chemistry Chemical Physics : PCCP·Thomas Teusch, Thorsten Klüner
May 10, 2019·The Journal of Chemical Physics·Benjamin Helmich-Paris
Feb 24, 2020·The Journal of Chemical Physics·David A KreplinHans-Joachim Werner
Jun 15, 2020·The Journal of Chemical Physics·Frank NeeseChristoph Riplinger
May 6, 2021·Inorganic Chemistry·Nicolaj KofodThomas Just Sørensen
Aug 7, 2021·Physical Chemistry Chemical Physics : PCCP·Abhishek Khedkar, Michael Roemelt
May 29, 2019·Journal of Chemical Theory and Computation·Benjamin Helmich-Paris

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