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Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNCThe quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbation estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10, 472 +/- 5, and 2051 +/- 10 cm(exp -1) for omega(sub 1), omega(sub 2), and omega(sub 3), respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental nu(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.
Document ID
19970023591
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lee, Timothy J.
(NASA Ames Research Center Moffett Field, CA United States)
Dateo, Christopher E.
(Eloret Corp. Palo Alto, CA United States)
Gazdy, Bela
(Emory Univ. Atlanta, GA United States)
Bowman, Joel M.
(Emory Univ. Atlanta, GA United States)
Date Acquired
August 17, 2013
Publication Date
January 1, 1993
Publication Information
Publication: The Journal of Physical Chemistry
Publisher: American Chemical Society
Volume: 97
Issue: 35
ISSN: 0022-3654
Subject Category
Inorganic And Physical Chemistry
Report/Patent Number
NAS 1.26:203710
NASA-CR-203710
Accession Number
97N72197
Funding Number(s)
CONTRACT_GRANT: NCC2-737
Distribution Limits
Public
Copyright
Public Use Permitted.
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