Ground states of BeC and MgC: A comparative multireference Brillouin-Wigner coupled cluster and configuration interaction study
Result description
The competing X3.SIGMA.- and 5.SIGMA.- states of the experimentally unknown alkaline-earth metal carbides BeC and MgC are examined with the multireference Brillouin-Wigner coupled cluster method restricted to single and double excitations (MRBW-CCSD). The results are compared against the traditional single-reference CCSD approach, as well as with other single and multireference methods. In both molecules, the CCSD 5.SIGMA.- <- X3.SIGMA.- energy difference is underestimated, leading to an "erroneous" ground-state prediction in BeC. The MRBW-CCSD method corrects this anomalous behavior, leading to fair agreement with multireference configuration interaction (MR-CI) predictions. Our results at the highest levels of theory are extrapolated to the basis setlimit, and the core/valence correlation is taken into account, leading to very accurate energetics and spectroscopic constants in both carbides.
Keywords
carbidesspectroscopic constantsmultireference configuration interactionmultireference coupled cluster
The result's identifiers
Result code in IS VaVaI
Result on the web
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DOI - Digital Object Identifier
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Alternative languages
Result language
angličtina
Original language name
Ground states of BeC and MgC: A comparative multireference Brillouin-Wigner coupled cluster and configuration interaction study
Original language description
The competing X3.SIGMA.- and 5.SIGMA.- states of the experimentally unknown alkaline-earth metal carbides BeC and MgC are examined with the multireference Brillouin-Wigner coupled cluster method restricted to single and double excitations (MRBW-CCSD). The results are compared against the traditional single-reference CCSD approach, as well as with other single and multireference methods. In both molecules, the CCSD 5.SIGMA.- <- X3.SIGMA.- energy difference is underestimated, leading to an "erroneous" ground-state prediction in BeC. The MRBW-CCSD method corrects this anomalous behavior, leading to fair agreement with multireference configuration interaction (MR-CI) predictions. Our results at the highest levels of theory are extrapolated to the basis setlimit, and the core/valence correlation is taken into account, leading to very accurate energetics and spectroscopic constants in both carbides.
Czech name
Základní stavy molekul BeC a MgC: Srovnávací studie metodami Multireferenční Brillouin-Wigner Coupled Cluster a konfigurační interakce
Czech description
Oběma metodami jsou studovány experimentálně neznámé stavy X3.SIGMA..SUP.-./SUP. a X5.SIGMA.- karbidů kovů alkalických zemin BeC a MgC. Výsledky jsou porovnány s výsledky tradiční jednoreferenční metody CCSD, jakož i s výsledky získanými jinými jednoreferenčními i multireferenčními metodami. Pro obě molekuly CCSD poskytuje příliš malý energetický rozdíl 5.SIGMA.- <- 3.SIGMA.-. Pro BeC dokonce určuje chybné pořadí těchto dvou stavů. Použití multireferenční metody Brillouin-Wigner CCSD vede k opravě tétochyby a poskytuje výsledky v dobré shodě s metodou multireferenční konfigurační interakce. Naše výsledky jsou extrapolovány na limitu použité báze a elektronová korelace vnitřních a valenčních elektronů je vzata v úvahu. Energetické a spektroskopické předpovědi pro oba karbidy jsou proto velmi přesné.
Classification
Type
Jx - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)
CEP classification
CF - Physical chemistry and theoretical chemistry
OECD FORD branch
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Result continuities
Project
OC D23.001: A European Laboratory for Multireference Quantum Chemical Methods
Continuities
Z - Vyzkumny zamer (s odkazem do CEZ)
Others
Publication year
2005
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
International Journal of Quantum Chemistry
ISSN
0020-7608
e-ISSN
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Volume of the periodical
102
Issue of the periodical within the volume
5
Country of publishing house
US - UNITED STATES
Number of pages
13
Pages from-to
762-774
UT code for WoS article
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EID of the result in the Scopus database
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Basic information
Result type
Jx - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)
CEP
CF - Physical chemistry and theoretical chemistry
Year of implementation
2005