Journal Article10.1080/00268978200100742
A simplified direct minimization of SCF energy for many-shell systems
S. Polezzo,P. Fantucci +1 more
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TL;DR: In this paper, a simplified version of the many-shell SCF theory is presented in which advantage is taken of the direct mixing between occupied and virtual orbitals and of the invariance to orthogonal mixing within each shell subspace.
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Abstract: A simplified version of the many-shell SCF theory is presented in which advantage is taken of the direct mixing between occupied and virtual orbitals and of the invariance to orthogonal mixing within each shell subspace. A vector gradient and a second derivative matrix of dimensions equal to the number of the occupied orbitals are used in a variable metric and Newton-Raphson algorithms to minimize the energy functional. Numerical tests are given for the 2II state (three shells) of CH and for the LiH molecule.
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A quadratically convergent multiconfiguration–self‐consistent field method with simultaneous optimization of orbitals and CI coefficients
TL;DR: In this article, a quadratically convergent MC-SCF procedure is described, which is based on the direct minimization of the energy, and the convergence radius is much improved by taking into account in the energy expansion those parts of third and higher order terms which account exactly for the orthonormality constraints imposed on the orbitals.
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MC-SCF. I. The multi-configuration self-consistent-field method
TL;DR: In this paper, the general multi-configuration self-consistent field (MC•SCF) method is presented with no restrictions on the types of configurations participating in the expansion of the total wave function.
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Ab initio Hartree-Fock instabilities in closed-shell molecular systems
TL;DR: The Hartree-Fock instability of twelve polyatomic systems is studied at theab initio level in this article, where the existence of these instabilities is discussed with respect to the location of low-lying excited states and to the weight of ionic structure.
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Exponential transformation of molecular orbitals: A quadratically convergent SCF procedure. I. General formulation and application to closed-shell ground states
TL;DR: In this paper, an exponential transformation of spin-orbitals is used to obtain the wave functions of SCF solutions, which obviates the use of Lagrangian multipliers.
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