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Influence of the choice of projection manifolds in the CASPT2 implementation

Yanai, Takeshi; Kurashige, Yuki; Saitow, Masaaki; Chalupský, Jakub; Lindh, Roland LU and Malmqvist, Per Åke LU (2016) In Molecular Physics
Abstract

The Complete Active Space Second-Order Perturbation Theory (CASPT2) is well-established as a high-accuracy electronic structure method. It was originally implemented in the early 1990s to an efficient computer code in the molcas program suite, and this implementation has been extensively used as a standard tool. Here, we report a comparison of it against two independent computer-aided implementations of the CASPT2 method, revealing that the CASPT2 energies provided by the original code of molcas (version 8 or earlier) are inconsistent with the predictions of the lately developed computer-aided implementations. It is shown that this error is associated with the projections of the first-order equation onto the fully internally contracted... (More)

The Complete Active Space Second-Order Perturbation Theory (CASPT2) is well-established as a high-accuracy electronic structure method. It was originally implemented in the early 1990s to an efficient computer code in the molcas program suite, and this implementation has been extensively used as a standard tool. Here, we report a comparison of it against two independent computer-aided implementations of the CASPT2 method, revealing that the CASPT2 energies provided by the original code of molcas (version 8 or earlier) are inconsistent with the predictions of the lately developed computer-aided implementations. It is shown that this error is associated with the projections of the first-order equation onto the fully internally contracted multireference bases which are partially inconsistent between the left- and right-hand sides. The degree of the errors is assessed by performing illustrative CASPT2 calculations. The errors in total CASPT2 energies are demonstrated to be negligible relative to chemical accuracy in many cases, while there is a difficult case where they may substantially alter chemical description. The incorporation of the consistent projections into molcas has been carried out, which is available in the version 8 sp1.

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author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
CASPT2, computer-aided programming, MOLCAS, Multireference theory
in
Molecular Physics
pages
9 pages
publisher
Taylor & Francis
external identifiers
  • scopus:85007311372
ISSN
0026-8976
DOI
10.1080/00268976.2016.1271152
language
English
LU publication?
yes
id
af2e5482-48bd-4ca9-8ff6-9869213e2d38
date added to LUP
2017-01-13 11:19:20
date last changed
2017-03-01 16:39:03
@article{af2e5482-48bd-4ca9-8ff6-9869213e2d38,
  abstract     = {<p>The Complete Active Space Second-Order Perturbation Theory (CASPT2) is well-established as a high-accuracy electronic structure method. It was originally implemented in the early 1990s to an efficient computer code in the molcas program suite, and this implementation has been extensively used as a standard tool. Here, we report a comparison of it against two independent computer-aided implementations of the CASPT2 method, revealing that the CASPT2 energies provided by the original code of molcas (version 8 or earlier) are inconsistent with the predictions of the lately developed computer-aided implementations. It is shown that this error is associated with the projections of the first-order equation onto the fully internally contracted multireference bases which are partially inconsistent between the left- and right-hand sides. The degree of the errors is assessed by performing illustrative CASPT2 calculations. The errors in total CASPT2 energies are demonstrated to be negligible relative to chemical accuracy in many cases, while there is a difficult case where they may substantially alter chemical description. The incorporation of the consistent projections into molcas has been carried out, which is available in the version 8 sp1.</p>},
  author       = {Yanai, Takeshi and Kurashige, Yuki and Saitow, Masaaki and Chalupský, Jakub and Lindh, Roland and Malmqvist, Per Åke},
  issn         = {0026-8976},
  keyword      = {CASPT2,computer-aided programming,MOLCAS,Multireference theory},
  language     = {eng},
  month        = {12},
  pages        = {9},
  publisher    = {Taylor & Francis},
  series       = {Molecular Physics},
  title        = {Influence of the choice of projection manifolds in the CASPT2 implementation},
  url          = {http://dx.doi.org/10.1080/00268976.2016.1271152},
  year         = {2016},
}