Cortez, Michael H., Brinkmann, Nicole R., Polik, William F., Taylor, Peter R., Bomble, Yannick J. and Stanton, John F. (2007) Factors contributing to the accuracy of harmonic force field calculations for water. Journal of Chemical Theory and Computation, Vol.3 (No.4). pp. 1267-1274. doi:10.1021/ct600347e

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Abstract

An analysis of the major factors affecting the accuracy of harmonic force field computations of water is presented. By systematically varying the level of approximation in the basis set, treatment of electron correlation, core electron correlation, and relativistic correction, the underlying sources of error in the computation of harmonic vibrational frequencies for water were quantified. The convergence error due to wavefunction description with a cc-pVQZ basis set in the absence of electron correlation was 1.6 cm(-1), as determined from extending the Hartree-Fock computations to larger basis sets. The convergence error due to neglecting higher-order electronic correlation terms than are included at the CCSD(T) level using the cc-pVTZ basis set was estimated to be 4.7 cm(-1), as determined from frequency calculations up to CCSDTQ for water and literature results up to CCSDTQP for diatomic molecules. The convergence error due to omitting higher-order diffuse functions than included in aug-cc-pVQZ was found to be 3.7 cm(-1), as determined by adding more diffuse functions in larger basis sets. The error associated with neglecting core electron correlation effects (i.e., "freezing" core electrons) was 5.0 cm(-1) and with neglecting relativistic effects was 2.2 cm(-1). Due to a cancellation among these various sources of error, the harmonic frequencies for H2O computed using the CCSD(T)/aug-cc-pVQZ model chemistry were on average within 2 cm(-1) of experimentally inferred vibrational frequencies.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Journal or Publication Title:	Journal of Chemical Theory and Computation
Publisher:	American Chemical Society
ISSN:	1549-9618
Official Date:	July 2007
Dates:	Date Event July 2007 Published
Volume:	Vol.3
Number:	No.4
Number of Pages:	8
Page Range:	pp. 1267-1274
DOI:	10.1021/ct600347e
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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