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The Generality of the GUGA MRCI Approach in COLUMBUS for Treating Complex Quantum Chemistry

Hans Lischka 1 Ron Shepard 2 Thomas Müller 3 Peter Szalay 4 Russell Pitzer 5 Adélia Aquino 6 Mayzza Araújo Do Nascimento 7 Mario Barbatti 8 Lachlan Belcher 9 Jean-Philippe Blaudeau 10 Itamar Borges 11 Scott Brozell 2 Emily Carter 12 Anita Das 13 Gergely Gidofalvi 14 Leticia González 15 William Hase 16 Gary Kedziora 17 Miklos Kertesz 18 Fábris Kossoski 8 Francisco Machado 19 Spiridoula Matsika 20 Silmar Do Monte 7 Dana Nachtigallova 21 Reed Nieman 22 Markus Oppel 23 Carol Parish 24 Felix Plasser 25 Rene Spada 19 Eric Stahlberg 26 Elizete Ventura 7 David Yarkony 27 Zhiyong Zhang 28
Abstract : The core part of the program system COLUMBUS allows highly efficient calculations using variational multireference (MR) methods in the framework of configuration interaction with single and double excitations (MR-CISD) and averaged quadratic coupled-cluster calculations (MR-AQCC), based on uncontracted sets of configurations and the graphical unitary group approach (GUGA). The availability of analytic MR-CISD and MR-AQCC energy gradients and analytic nonadiabatic couplings for MR-CISD enables exciting applications including, e.g., investigations of π-conjugated biradicaloid compounds, calculations of multitudes of excited states, development of diabatization procedures, and furnishing the electronic structure information for on-the-fly surface nonadiabatic dynamics. With fully variational uncontracted spin-orbit MRCI, COLUMBUS provides a unique possibility of performing high-level calculations on compounds containing heavy atoms up to lanthanides and actinides. Crucial for carrying out all of these calculations effectively is the availability of an efficient parallel code for the CI step. Configuration spaces of several billion in size now can be treated quite routinely on standard parallel computer clusters. Emerging developments in COLUMBUS, including the all configuration mean energy multiconfiguration self-consistent field method and the graphically contracted function method, promise to allow practically unlimited configuration space dimensions. Spin density based on the GUGA approach, analytic spin-orbit energy gradients, possibilities for local electron correlation MR calculations, development of general interfaces for nonadiabatic dynamics, and MRCI linear vibronic coupling models conclude this overview.
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Submitted on : Tuesday, May 19, 2020 - 9:39:33 AM
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Hans Lischka, Ron Shepard, Thomas Müller, Peter Szalay, Russell Pitzer, et al.. The Generality of the GUGA MRCI Approach in COLUMBUS for Treating Complex Quantum Chemistry. Journal of Chemical Physics, American Institute of Physics, 2020, 152 (13), pp.134110. ⟨10.1063/1.5144267⟩. ⟨hal-02612344⟩



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