The balance between theoretical method and basis set quality: A systematic study of equilibrium geometries, dipole moments, harmonic vibrational frequencies, and infrared intensities

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.465764· OSTI ID:6235240

Thomas, J R; DeLeeuw, B J; Vacek, G; Crawford, T D; Yamaguchi, Y; Schaefer, III, H F ^[1]

---

1. Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia, 30602 (United States)

Analytic gradient methods have been used to predict the equilibrium geometries, dipole moments, harmonic vibrational frequencies, and infrared (IR) intensities of HCN, HNC, CO[sub 2], CH[sub 4], NH[sub 4][sup +], HCCH, H[sub 2]O, H[sub 2]CO, NH[sub 3], and FCCH at the self-consistent-field (SCF), the single and double excitations configuration interaction (CISD), the single and double excitations coupled-cluster (CCSD), and the single, double, and perturbative triple excitations coupled-cluster [CCSD(T)] levels of theory. All studies were performed using a triple zeta plus double polarization (TZ2P) basis set and a TZ2P basis set augmented with one set of higher angular momentum functions [TZ (2[ital df],2[ital pd])]. The predicted equilibrium geometries, dipole moments, harmonic vibrational frequencies, and IR intensities were compared to available experimental values. The geometries were predicted accurately at the highest levels of theory. Most of the dipole moments were found to agree favorably with experiment. With the TZ2P basis set, the average absolute errors in harmonic vibrational frequencies with respect to experiment were 9.9%, 3.8%, 1.5%, and 2.3% for the SCF, CISD, CCSD, and CCSD(T) methods, respectively. With the TZ(2[ital df],2[ital pd]) basis set, the four methodologies yielded average absolute errors of 10.3%, 6.3%, 3.7%, and 2.2%, respectively. When the absolute errors for bending modes of triply bonded molecules and the [ital a][sub 1] umbrella mode of NH[sub 3] were excluded from the previous two sets of averages, the TZ2P average errors became 7.3% (SCF), 3.0% (CISD), 1.1% (CCSD), and 1.1% [CCSD(T)], and the TZ(2[ital df],2[ital pd]) average errors became 7.4% (SCF), 3.5% (CISD), 1.5% (CCSD), and 0.6% [CCSD(T)]. Theoretical IR intensities were generally close to given experimental values.

• DOE Contract Number: FG09-87ER13811
• OSTI ID: 6235240
• Journal Information: Journal of Chemical Physics; (United States), Vol. 99:1; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AMMONIA
PHYSICAL PROPERTIES
CARBON DIOXIDE
CYANIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
METHANE
NITROGEN CARBIDES
NITROGEN HYDRIDES
ORGANIC FLUORINE COMPOUNDS
WATER
AMPLITUDES
BINDING ENERGY
CARBONATES
CONFIGURATION INTERACTION
DIPOLE MOMENTS
ELECTRON CORRELATION
EQUILIBRIUM
GEOMETRY
HARMONICS
INFRARED SPECTRA
MOLECULAR IONS
VIBRATIONAL STATES
ALKANES
CARBIDES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLES
CORRELATIONS
ENERGY
ENERGY LEVELS
EXCITED STATES
HYDRIDES
IONS
MATHEMATICS
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OSCILLATIONS
OXIDES
OXYGEN COMPOUNDS
SPECTRA
664100* - Theory of Electronic Structure of Atoms & Molecules- (1992-)