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The Effect of Approximating Some Molecular Integrals in Coupled-Cluster Calculations: Fundamental Frequencies and Rovibrational Spectroscopic Constants of CyclopropenylideneThe singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, denoted CCSD(T), has been used, in conjunction with approximate integral techniques, to compute highly accurate rovibrational spectroscopic constants of cyclopropenylidene, C3H2. The approximate integral technique was proposed in 1994 by Rendell and Lee in order to avoid disk storage and input/output bottlenecks, and today it will also significantly aid in the development of algorithms for distributed memory, massively parallel computer architectures. It is shown in this study that use of approximate integrals does not impact the accuracy of CCSD(T) calculations. In addition, the most accurate spectroscopic data yet for C3H2 is presented based on a CCSD(T)/cc-pVQZ quartic force field that is modified to include the effects of core-valence electron correlation. Cyclopropenylidene is of great astronomical and astrobiological interest because it is the smallest aromatic ringed compound to be positively identified in the interstellar medium, and is thus involved in the prebiotic processing of carbon and hydrogen. The singles and doubles coupled-cluster method that includes a perturbational estimate of
Document ID
20050182131
Acquisition Source
Headquarters
Document Type
Preprint (Draft being sent to journal)
Authors
Lee, Timothy J.
(NASA Ames Research Center Moffett Field, CA, United States)
Dateo, Christopher E.
(Eloret Corp. Moffett Field, CA, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Subject Category
Computer Programming And Software
Meeting Information
Meeting: Virginia Tech Universities Dept. of Chemistry
Location: Virginia
Country: United States
Start Date: March 1, 2005
Funding Number(s)
PROJECT: Proj. 21-302-15-11
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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