Towards multireference equivalents of the G2 and G3 methods
dc.contributor.author | Solling, Theis I. | |
dc.contributor.author | Smith, David M. | |
dc.contributor.author | Radom, Leo | |
dc.contributor.author | Freitag, Mark A. | |
dc.contributor.author | Gordon, Mark S. | |
dc.date.accessioned | 2015-10-20T00:44:58Z | |
dc.date.available | 2015-10-20T00:44:58Z | |
dc.date.issued | 2001-11-15 | |
dc.date.updated | 2015-12-12T09:46:05Z | |
dc.description.abstract | The effect of replacing the standard single-determinant reference wave functions in variants of G2 and G3 theory by multireference (MR) wave functions based on a full-valence complete active space has been investigated. Twelve methods of this type have been introduced and comparisons, based on a slightly reduced G2-1 test set, are made both internally and with the equivalent single-reference methods. We use CASPT2 as the standard MR-MP2 method and MRCl+Q as the higher correlation procedure in these calculations. We find that MR-G2(MP2,SVP), MR-G2(MP2), and MR-G3(MP2) perform comparably with their single-reference analogs, G2(MP2,SVP), G2(MP2), and G3(MP2), with mean absolute deviations (MADs) from the experimental data of 1.41, 1.54, and 1.23 kcal mol−1, compared with 1.60, 1.59, and 1.19 kcal mol−1, respectively. The additivity assumptions in the MR-Gn methods have been tested by carrying out MR-G2/MRCI+Q and MR-G3/MRCI+Q calculations, which correspond to large-basis-set MRCI+Q+ZPVE+HLC calculations. These give MADs of 1.84 and 1.58 kcal mol−1, respectively, i.e., the agreement with experiment is somewhat worse than that obtained with the MR-G2(MP2) and MR-G3(MP2) methods. In a third series of calculations, we have examined pure MP2 and MR-MP2 analogs of the G2 and G3 procedures by carrying out large-basis-set MP2 and CASPT2(+ZPVE+HLC) calculations. The resultant methods, which we denote G2/MP2, G3/MP2, MR-G2/MP2, and MR-G3/MP2, give MADs of 4.19, 3.36, 2.01, and 1.66 kcal mol−1, respectively. Finally, we have examined the effect of using MCQDPT2 in place of CASPT2 in five of our MR-Gn procedures, and find that there is a small but consistent deterioration in performance. Our calculations suggest that the MR-G3(MP2) and MR-G3/MP2 procedures may be useful in situations where a multireference approach is desirable. | |
dc.description.sponsorship | The authors would also like to thank the National Science Foundation International Division for providing travel funds to ~M.S.G. and M.A.F.! and the National Science Foundation Chemistry Division for supporting the research. | en_AU |
dc.identifier.issn | 0021-9606 | en_AU |
dc.identifier.uri | http://hdl.handle.net/1885/15978 | |
dc.publisher | American Institute of Physics (AIP) | |
dc.rights | http://www.sherpa.ac.uk/romeo/issn/0021-9606..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 20/10/15). Copyright 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at https://doi.org/10.1063/1.1411998 | |
dc.source | The Journal of Chemical Physics | |
dc.subject | Keywords: Calculations; Mathematical models; Numerical methods; Thermodynamics; Mean absolute deviation; Multireference equivalents; Multireference wave function; Physical chemistry | |
dc.title | Towards multireference equivalents of the G2 and G3 methods | |
dc.type | Journal article | |
local.bibliographicCitation.issue | 19 | en_AU |
local.bibliographicCitation.lastpage | 8772 | en_AU |
local.bibliographicCitation.startpage | 8758 | en_AU |
local.contributor.affiliation | Solling, Theis, College of Physical and Mathematical Sciences, CPMS Research School of Chemistry, RSC General, The Australian National University | en_AU |
local.contributor.affiliation | Trebeck, Katherine, College of Physical and Mathematical Sciences, CPMS Research School of Chemistry, RSC General, The Australian National University | en_AU |
local.contributor.affiliation | Radom, Leo, College of Physical and Mathematical Sciences, CPMS Research School of Chemistry, RSC General, The Australian National University | en_AU |
local.contributor.affiliation | Freitag, M, Creighton University, United States of America | en_AU |
local.contributor.affiliation | Gordon, Mark S, Iowa State University, United States of America | en_AU |
local.contributor.authoruid | T447 | en_AU |
local.description.notes | Imported from ARIES | en_AU |
local.description.refereed | Yes | |
local.identifier.absfor | 030602 | en_AU |
local.identifier.ariespublication | MigratedxPub25972 | en_AU |
local.identifier.citationvolume | 115 | en_AU |
local.identifier.doi | 10.1063/1.1411998 | en_AU |
local.identifier.scopusID | 2-s2.0-0035891058 | |
local.identifier.uidSubmittedBy | u3488905 | en_AU |
local.publisher.url | https://www.aip.org/ | en_AU |
local.type.status | Published Version | en_AU |
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