A benchmark coupled-cluster single, double, and triple excitation (CCSDT) study of the structure and harmonic vibrational frequencies of the ozone molecule

✍ Scribed by John D. Watts; John F. Stanton; Rodney J. Bartlett

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 403 KB
• Volume: 178
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(91)87004-u

✦ Synopsis

We. report a benchmark calculation of the structure and harmonic vibrational frequencies of the ozone molecule using the full coupled-cluster single, double, and tripleexcitation model (CCSDT) with a DZP basis set. The resultsoffer a definitive reference for assessing the accuracy of methods which approximate the effects of TX. For the bending and symmetric stretching frequencies, CCSD(T), CCSDT-2, and CCSDT-3 all give results close to CCSDT. For the asymmetric stretching frequency, however, the values predicted by the CCSD(T) and CCSDT-2 models are respeclively about 100 cm-' lower and higher than the CCSDT value, while the CCSDT-3 value exceeds the CCSDT value by 41 cm-'. It is suggested that effects ofconnected quadruple excitations ( T4) and higher cluster operators may have a significant effect on the asymmetric stretching frequency.