A new semi-empirical method of correcting large-scale configuration interaction calculations for incomplete dynamic correlation of electrons

We present a protocol based on unitary transformations of molecular orbitals to reduce the number of non-vanishing coefficients of spin-adapted configuration interaction expansions. Methods that exploit the sparsity of the Hamiltonian matrix and compactness of its eigensolutions, such as the FCIQMC algorithm in its spin-adapted implementation, are well suited to this protocol. The wave function compression resulting from this approach is particularly attractive for anti-ferromagnetically coupled polynuclear spin systems, such as transition metal cubanes in bio-catalysis and, Mott and charge-transfer insulators in solid state physics. Active space configuration interaction calculations on the stretched N2 and square N4 compounds, the chromium dimer, and a [Fe2S2] model system are presented as a proof-of-concept. For the Cr2 case large and intermediate bond distances are discussed, showing that the approach is effective in cases where static and dynamic correlation are equally important. The [Fe2S2] case shows the general applicability of the method.

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Erzeugung und Untersuchung des Cyclopentadienons mit der Methode der temperaturabhängigen Photoelektronenspektroskopie / Preparation and Investigation of Cyclopentadienone by Variable Temperature Photoelectron Spectroscopy (VTPES)

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-0320 ◽

1978 ◽

Vol 33 (3) ◽

pp. 383-385 ◽

Cited By ~ 1

Author(s):

Veit Eck ◽

Günther Lauer ◽

Armin Schweig ◽

Walter Thiel ◽

Hans Vermeer

Keyword(s):

Dicarboxylic Acid ◽

Gas Phase ◽

Configuration Interaction ◽

Photoelectron Spectroscopy ◽

Large Scale ◽

Variable Temperature ◽

Acid Anhydride ◽

Selection Procedures ◽

Scale Perturbation ◽

Configuration Interaction Calculations

AbstractUsing our VTPES technique cyclopentadienone is generated in the gas phase at 500-600 °C from the three different precursors cyclobutene-3,4-dicarboxylic acid anhydride, o-phenylene sulfite and o-benzoquinone and its PE spectrum is recorded. The PE spectrum and also the PE spectra of the various precursors as well as of the cyclopentadienone dimer are interpreted on the basis of our recently developed PERTCI method (i. e. performing large scale perturbation configuration interaction calculations in connection with selection procedures). The agreement between measured and calculated ionization potentials is good.

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Large-scale first principles configuration interaction calculations of optical absorption in aluminum clusters

Physical Chemistry Chemical Physics ◽

10.1039/c4cp02232g ◽

2014 ◽

Vol 16 (38) ◽

pp. 20714-20723 ◽

Cited By ~ 14

Author(s):

Ravindra Shinde ◽

Alok Shukla

Keyword(s):

Optical Absorption ◽

Configuration Interaction ◽

First Principles ◽

Large Scale ◽

Aluminum Clusters ◽

Configuration Interaction Calculations

Optical absorption in Al clusters.

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A global approach to perform large-scale configuration–interaction calculations

Canadian Journal of Physics ◽

10.1139/cjp-2016-0886 ◽

2017 ◽

Vol 95 (9) ◽

pp. 878-883

Author(s):

Franck Gilleron ◽

Jean-Christophe Pain

Keyword(s):

Configuration Interaction ◽

Large Scale ◽

Basis Set ◽

Hamiltonian Matrix ◽

Global Approach ◽

Minimal Set ◽

Total Strength ◽

Averaged Hamiltonian ◽

Structure Calculations ◽

Configuration Interaction Calculations

We present a global approach that allows one to tackle cumbersome configuration–interaction calculations. The method is based on the use of approximate configuration-averaged Hamiltonian matrix elements that can be expressed in compact form as a combination of Slater integrals. With some assumptions, we show that the Hamiltonian matrix to be diagonalized may be reduced to a size equivalent to the number of configurations in the basis set. The approach can be used to estimate shifts of configuration average energies and changes in the total strength of transition arrays. The method is also well suited to work out roughly difficult configuration–interaction calculations, to determine the minimal set of interacting configurations to be used in actual fine-structure calculations.

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