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Calibration of Cholesky Auxiliary Basis Sets for Multiconfigurational Perturbation Theory Calculations of Excitation Energies
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2010 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 3, 747-754 p.Article in journal (Refereed) Published
Abstract [en]

The accuracy of auxiliary basis sets derived from Cholesky decomposition of two-electron integrals is assessed for excitation energies calculated at the state-average complete active space self-consistent field (CASSCF) and multiconfigurational second order perturbation theory (CASPT2) levels of theory using segmented as well as generally contracted atomic orbital basis sets. Based on 196 valence excitations in 26 organic molecules and 72 Rydberg excitations in 3 organic molecules, the results show that Cholesky auxiliary basis sets can be used without compromising the accuracy of the multiconfigurational methods. Specifically, with a decomposition threshold of 10(-4) au, the mean error due to the Cholesky auxiliary basis set is 0.001 eV, or smaller, decreasing with increasing atomic orbital basis set quality.

Place, publisher, year, edition, pages
2010. Vol. 6, no 3, 747-754 p.
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-141205DOI: 10.1021/ct900612kOAI: oai:DiVA.org:uu-141205DiVA: diva2:385232
Available from: 2011-01-11 Created: 2011-01-11 Last updated: 2015-03-13Bibliographically approved
In thesis
1. Extending the Reach of Accurate Wavefunction Methods
Open this publication in new window or tab >>Extending the Reach of Accurate Wavefunction Methods
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Multiconfigurational quantum chemistry methods, and especially the multiconfigurational self-consistent field (MCSCF) and multireference perturbation theory (MRPT2), are powerful tools, particularly suited to the accurate modeling of photochemical processes and transition metal catalysis. However, they are limited by their high computational cost compared to other methods, especially density functional theory. Moreover, there are areas where they would be expected to perform well, but where they are not applied due to lack of experience.

This thesis addresses those issues. First, the efficiency of the Cholesky decomposition approximation to reduce the cost of MCSCF and MRPT2 without sacrificing their accuracy is demonstrated. This then motivates the extension of the Cholesky approximation to the computation of MCSCF nuclear gradients, thus strongly improving the ability to perform MCSCF non-adiabatic molecular dynamics. Typically, a tenfold speed-up is observed allowing dynamic simulation of larger systems or over longer times.

Finally, multiconfigurational methods are applied to the computation of X-ray spectra of transition metal complexes. The importance of the different parameters in the calculation is systematically investigated, laying the base for wider applications of those accurate methods in the modeling of X-ray spectroscopy. A tool to analyze the resulting spectrum in terms of molecular orbitals is also presented, strengthening the interplay between theory and experiments.

With these developments and other significant ones that have happened in recent years, multiconfigurational methods can now reach new grounds and contribute to important new discoveries

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 75 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1228
Quantum chemistry, Density fitting, CASSCF, Analytical gradients, Photochemistry, X-ray spectroscopy
National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
urn:nbn:se:uu:diva-243573 (URN)978-91-554-9168-0 (ISBN)
Public defence
2015-03-31, Siegbahnsalen, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2015-03-10 Created: 2015-02-10 Last updated: 2015-04-14Bibliographically approved

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Delcey, Mickael GLindh, Roland
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