Quasi-bond orbitals from maximum-localization hybrids for ab initio CI calculations

Angeli, Celestino; Re, Giuseppe Del; Persico, Maurizio

doi:10.1016/0009-2614(94)01415-r

Cited by 24 publications

(28 citation statements)

References 18 publications

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“…The canonical (delocalized) Self Consistent Fied (SCF) orbitals computed with the Atomic Natural Orbital (ANO) basis set [26] were localized following an a priori strategy. [27] This approach allows the electronic wavefunctions to be described in terms close to the Lewis' view [28] and has been used to unravel the nature of complex wavefunctions. [29] Supporting Information (see footnote on the first page of this article): Figures depicting luminescent spectra, TGA curves, cyclic voltammograms and crystal packing along with tables representing CSD reference codes and details of DFT calculations.…”

Section: X-ray Crystallographymentioning

confidence: 99%

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)

et al. 2012

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Section: X-ray Crystallographymentioning

confidence: 99%

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)

et al. 2012

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“…It was shown in previous papers 2, 9 that the Fock and overlap matrices of a molecule can be put in a quasi‐localized form before computation of the canonical orbitals by (a), orthogonalizing the pertinent Gaussian basis set in such a way that its elements have the properties of typical atomic orbitals, and (b) determining from the latter hybrid atomic orbitals meeting appropriate physical conditions. In the overlap and Fock matrices referred to the basis of hybridized atomic orbitals, large off‐diagonal elements are associated with bonds.…”

Section: Molecular Structure–property Relations and Ab Initio Orbimentioning

confidence: 99%

“…The overlap‐based procedure to be compared with the above is an application to multiple–ζ ab initio computations 2, 9 of previous work of this group 17, 18 and is based on the maximum bond‐overlap (MB) criterion. (For recent work on the overlap–energy relation and the maximum‐overlap principle, cf.…”

Section: Localization Proceduresmentioning

confidence: 99%

MO‐LCAO approach and ab initio computations

Capobianco

2006

Int J of Quantum Chemistry

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ABSTRACT:The physical reliability and foundations of the Hund-Hückel MO-LCAO model, in which a molecular orbital (MO) is represented as a linear combination of atomic orbitals (LCAO), are examined in light of ab initio self-consistent field (SCF) computations with bases of various sizes. It is shown that appropriate linear transformations of the basis make evident a substructure of the relevant ab initio matrices and vectors that justifies the physical assumptions on which the MO-LCAO model rests. The main conceptual aspects, viz. hydrogen-like atomic orbitals, hybrids, localized orbitals, give a coherent picture, and the numerical data show that the contributions to occupied orbital energies ignored in the MO-LCAO model are actually small enough to justify their neglect in chemical structure studies. The numerical parameter values can therefore be read quantitatively in the ab initio results and the importance of the approximations made estimated. These conclusions have been drawn from studies on a variety of molecules with first-and second-row atoms. The well-established transferability of group properties in molecules suggests that they are generally valid. The claim that hybrids are method-independent, and therefore features of chemical reality at the orbital level, is discussed due to its relevance for comparisons of the stability of chemical bonds based on overlap. Of course, further work on questions such as electronegativities and promotion is needed.

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“…Several methods are using a posteriori relocalizing unitary transformations, for instance the methods of Boys, 17 Edminston and Ruedenberg, 18 Pipek, 19 and Angeli et al, 20 which define an intrinsic criterion of localization ͑i.e., they maximize a localization function͒. Relocalizations that use an extrinsic criterion 3 of localization ͑such as projecting localized MOs on the canonical ones͒ work equally well.…”

Section: B a Priori Methods: The Generation Of Localized Scf Orbitalsmentioning

confidence: 99%

Direct generation of local orbitals for multireference treatment and subsequent uses for the calculation of the correlation energy

Maynau

Evangelisti

Guihéry

et al. 2002

The Journal of Chemical Physics

115

123

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We present a method that uses the one-particle density matrix to generate directly localized orbitals dedicated to multireference wave functions. On one hand, it is shown that the definition of local orbitals making possible physically justified truncations of the CAS ͑complete active space͒ is particularly adequate for the treatment of multireference problems. On the other hand, as it will be shown in the case of bond breaking, the control of the spatial location of the active orbitals may permit description of the desired physics with a smaller number of active orbitals than when starting from canonical molecular orbitals. The subsequent calculation of the dynamical correlation energy can be achieved with a lower computational effort either due to this reduction of the active space, or by truncation of the CAS to a shorter set of references. The ground-and excited-state energies are very close to the current complete active space self-consistent field ones and several examples of multireference singles and doubles calculations illustrate the interest of the procedure.

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Quasi-bond orbitals from maximum-localization hybrids for ab initio CI calculations

Cited by 24 publications

References 18 publications

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)

MO‐LCAO approach and ab initio computations

Direct generation of local orbitals for multireference treatment and subsequent uses for the calculation of the correlation energy

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Quasi-bond orbitals from maximum-localization hybrids for ab initio CI calculations

Cited by 24 publications

References 18 publications

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd2X7]3– Anions (X = Cl/Br)

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd2X7]3– Anions (X = Cl/Br)

MO‐LCAO approach and ab initio computations

Direct generation of local orbitals for multireference treatment and subsequent uses for the calculation of the correlation energy

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Product

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“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)

“Caging” Anions through Crystal Engineering to Avoid Polymerization: Structural, Conformational and Theoretical Investigations of New Halocadmate [Cd₂X₇]^3– Anions (X = Cl/Br)