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Journal ArticleDOI

Coriolis interaction and anharmonic potential function of ozone from the microwave spectra in the excited vibrational states

01 Mar 1970-Journal of Molecular Spectroscopy (Academic Press)-Vol. 33, Iss: 3, pp 538-551
TL;DR: In this article, the microwave absorption spectra of ozone were identified in the excited vibrational states with v1 = 1, v2 = 1 and 2, and v3 = 1.
About: This article is published in Journal of Molecular Spectroscopy.The article was published on 1970-03-01. It has received 222 citations till now. The article focuses on the topics: Excited state.
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TL;DR: In this article, the essential aspects of coupled-cluster theory are explained and illustrated with informative numerical results, showing that the theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules.
Abstract: Today, coupled-cluster theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules. Though it was originally proposed for problems in physics, it has seen its greatest development in chemistry, enabling an extensive range of applications to molecular structure, excited states, properties, and all kinds of spectroscopy. In this review, the essential aspects of the theory are explained and illustrated with informative numerical results.

2,667 citations

Journal ArticleDOI
TL;DR: In this article, a new hybrid exchange-correlation functional, denoted B97-2, was derived from correlated ab initio electron densities, and the potentials were examined graphically and used in conjunction with conventional thermochemical data to determine a new functional.
Abstract: Multiplicative potentials, appropriate for adding to the non-multiplicative fractional orbital exchange term in the Kohn–Sham equations, are determined from correlated ab initio electron densities. The potentials are examined graphically and are used in conjunction with conventional thermochemical data to determine a new hybrid exchange-correlation functional, denoted B97-2. Calculations using B97-2 are compared with those from (a) the B97-1 functional [J. Chem. Phys. 109, 6264 (1998)], which has the same functional form and fraction of orbital exchange, but was fitted to just thermochemical data; and (b) the widely used B3LYP functional [J. Chem. Phys. 98, 5648 (1993)]. B97-2 atomization energies are close to those from B97-1; total electronic energies and ionization potentials are less accurate, but remain an improvement over B3LYP. Molecular structures from all three functionals are comparable. Static isotropic polarizabilities improve from B3LYP to B97-1 to B97-2; the B97-2 functional underestimates experimental values, which is consistent with the neglect of zero-point vibrational corrections. NMR shielding constants—determined as the conventional second derivative of the electronic energy—improve from B3LYP to B97-1 to B97-2. Shieldings determined directly from these DFT electron densities using the recently proposed MKS approach [Chem. Phys. Lett. 337, 341 (2001)] are two to three times more accurate than the conventional shieldings, and exhibit an analogous improvement across the three functionals. Classical reaction barriers for sixteen chemical reactions improve significantly from B3LYP to B97-1 to B97-2. The introduction of multiplicative potentials into semi-empirical hybrid functional development therefore appears beneficial.

498 citations

Book ChapterDOI
Ian Mills1
01 Jul 1972

485 citations

Journal ArticleDOI
TL;DR: In this paper, a systematic investigation has been carried out of the accuracy of molecular equilibrium structures of 19 small closed-shell molecules containing first-row atoms as predicted by the following standard electronic ab initio models: Hartree-Fock (HF) theory, Mo/ller-Plesset theory to second, third, and fourth orders (MP2, MP3, and MP4), coupled-cluster singles and doubles (CCSD) theory; CCSD theory with perturbational triples corrections [CCSD(T)], and the configuration-interaction
Abstract: A systematic investigation has been carried out of the accuracy of molecular equilibrium structures of 19 small closed-shell molecules containing first-row atoms as predicted by the following standard electronic ab initio models: Hartree–Fock (HF) theory, Mo/ller–Plesset theory to second, third, and fourth orders (MP2, MP3, and MP4), coupled-cluster singles and doubles (CCSD) theory; CCSD theory with perturbational triples corrections [CCSD(T)], and the configuration-interaction singles and doubles (CISD) model. For all models, calculations were carried out using the correlation-consistent polarized valence double-zeta (cc-pVDZ) basis, the correlation-consistent polarized valence triple-zeta (cc-pVTZ) basis, and the correlation-consistent polarized valence quadruple-zeta (cc-pVQZ) basis. Improvements in the basis sets shorten the bond distances at all levels. Going from cc-pVDZ to cc-pVTZ, bond distances are on the average reduced by 0.8 pm at the Hartree–Fock level and by 1.6 pm at the correlated levels. From cc-pVTZ to cc-pVQZ, the contractions are about ten times smaller and the cc-pVTZ basis set appears to yield bond distances close to the basis-set limit for all models. The models HF, MP2, and CCSD(T) give improved accuracy at increased computational cost. The accuracy of the Mo/ller–Plesset series oscillates, with MP3 being considerably less accurate than MP2 and MP4. The MP2 geometries are remarkably accurate, being only very slightly improved upon at the MP4 level for the cc-pVQZ basis. The CCSD equilibrium structures are only moderately accurate, being intermediate between MP2 and MP3. The accuracy of the CCSD(T) model, in contrast, is high and comparable to that observed in most experimental studies and it has been used to challenge the experimentally determined equilibrium structure of HNO. The CISD wave function provides structures of low quality.

305 citations

References
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527 citations

Journal ArticleDOI
TL;DR: In this paper, a general formula for inertia defect of a molecule is presented following Nielsen's theory of vibration-rotation interaction, simplified by the use of general properties of 1 matrix which transforms the normal coordinates to the Cartesian coordinates.

275 citations

Journal ArticleDOI
TL;DR: In this paper, the microwave spectra of the SO2 molecule were measured in the first excited states of all the normal vibrations as well as in the second excited state of the ν2 vibration.

139 citations

Journal ArticleDOI
TL;DR: In this paper, four low-J rotational transitions of 0316 have been measured in the region from 42 to 118 kmc and the rotational spectroscopic constants found are A = 106,530.0±1.1 Mc, B = 13,349.06±0.06 Mc, C = 11,834.3±1 Mc.
Abstract: Four low‐J rotational transitions of 0316 have been measured in the region from 42 to 118 kmc. The rotational spectroscopic constants found are A = 106,530.0±1.1 Mc, B = 13,349.06±0.06 Mc, C = 11,834.3±1.1 Mc. The oxygen nuclei form an isosceles triangle with an apex angle of 116°49′±30′, and the two equal internuclear distances are 1.278±0.003A. From the Stark splitting of the 20,2→11,1 transition the dipole moment is 0.53±0.02 debye. Zeeman splittings of this transition show that ozone is not significantly paramagnetic.

96 citations

Journal ArticleDOI
TL;DR: In this article, 14 bands of ozone between 500 and 3300 cm −1 have been identified and values of the vibrational anharmonic constants determined and the integrated band absorptances of many of these bands have been measured from spectra of a 32-m path of ozone-oxygen mixtures containing up to 30 atm cm O ǫ near 25°C.

91 citations