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Hijikata, Katsunori

doi:10.1103/revmodphys.32.445

Cited by 16 publications

(3 citation statements)

References 2 publications

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“…Molecules containing two or more electronegative atoms have generally provided significant challenges to attempts to provide a theoretical basis for understanding their chemistry or extending knowledge of their properties. This challenge first became apparent when Hijikata showed that F 2 was not bound in the Hartree−Fock approximation, a result which has been duplicated for a number of molecules containing F and Cl. Although Das and Wahl were able to obtain good results using a carefully selected multiconfiguration wave function, accurate results from a reasonably systematic approach were not obtained until it was possible to carry out complete active space (CAS) SCF and large scale multireference CI (MRCI) treatments.…”

Section: Introductionmentioning

confidence: 99%

Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Phillips

Quelch

1996

J. Phys. Chem.

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A series of normal-valent compounds of potential interest with respect to atmospheric chlorine chemistry have been investigated using MCSCF ab initio methods with a good basis set. Comparisons of total energies of the compounds of interest with those of the radical precursors for complete active space wave functions including the bonding and antibonding orbitals of the molecules and the open shell orbitals of the radicals indicate that HOOCl, HOOOCl, and ClOOOCl are stable. Similar results for the compounds HOOH, ClOOCl, and HOOOH, which have been the subject of experimental or previous, more comprehensive, theoretical investigations, are presented for comparison. The predictions of stability for HOOCl and HOOOCl are of particular interest. HOOCl, which is the logical intermediate in the forward and backward reactions between HO + ClO and HOO + Cl, may be stabilized under some atmospheric and laboratory conditions. The role of HOOCl as an intermediate and the fact that the HOOCl adduct might be stabilized in certain parts of the stratosphere were suggested previously by Weissman et al. Also, Stimpfle et al. discussed HOOOCl as a possible intermediate in the HOO + ClO reaction but concluded on the basis of Benson's group additivity rules that its dissociation energy was probably too small for the molecule to be stable. The present results indicate that HOOOCl is sufficiently stable to be formed under some stratospheric conditions. At the MCSCF level of theory, HOOCl is predicted to have an electronic binding energy intermediate between those of ClOOCl and HOOH, while HOOOCl and ClOOOCl are predicted to have binding energies similar to that of ClOOCl.

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Section: Introductionmentioning

confidence: 99%

Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Phillips

Quelch

1996

J. Phys. Chem.

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“…The F 2 molecule represents a weakly bound system, and the Hartree−Fock-level PECs, at either the RHF or UHF level, are purely repulsive. , In reaction 5, this reactant molecule, as well as the transition complex HF 2 (TS), shows the largest MR effect among the systems considered in this work (cf. Table ).…”

Section: Resultsmentioning

confidence: 99%

Reduced Multireference Coupled-Cluster Method: Barrier Heights for Heavy Atom Transfer, Nucleophilic Substitution, Association, and Unimolecular Reactions

Paldus

2007

J. Phys. Chem. A

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The recently developed reduced multireference coupled-cluster method with singles and doubles (RMR CCSD) that is perturtatively corrected for triples [RMR CCSD(T)] is employed to compute the forward and reverse barrier heights for 19 non-hydrogen-transfer reactions. The method represents an extension of the conventional single-reference (SR) CCSD(T) method to multireference situations. The results are compared with a benchmark database, which is essentially based on the SR CCSD(T) results. With the exception of seven cases, the RMR CCSD(T) results are almost identical with those based on SR CCSD(T), implying the abatement of MR effects at the SD(T) level relative to the SD level. Using the differences between the RMR CCSD(T) and CCSD(T) barrier heights as a measure of MR effects, modified values for barrier heights of studied reactions are given.

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“…At the UHF level it is not even bound. 25 Nonetheless, the dynamical correlation in F 2 is appreciable. In fact, the full valence space CAS SCF yields only half of the binding energy.…”

Section: B the F 2 Moleculementioning

confidence: 99%

Reduced multireference couple cluster method. II. Application to potential energy surfaces of HF, F2, and H2O

Li¹,

Paldus²

1998

The Journal of Chemical Physics

174

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Performance of the general-model-space state-universal coupled-cluster method Can ordinary single-reference coupled-cluster methods describe potential energy surfaces with nearly spectroscopic accuracy? The renormalized coupled-cluster study of the vibrational spectrum of HF The so-called reduced multireference ͑RMR͒ coupled cluster method restricted to singly and doubly excited clusters ͑CCSD͒ ͓see X. Li and J. Paldus, J. Chem. Phys. 107, 6257 ͑1997͔͒ is employed to compute potential energy surfaces for the HF, F 2 and H 2 O molecules over a wide range of geometries using basis sets of a double zeta ͑DZ͒ and DZ plus polarization ͑DZP͒ quality. The RMR-CCSD method belongs to a class of externally corrected CCSD approaches, which rely on a suitable non-CC wave function that is flexible enough to describe the dissociation process at hand and is used as a source of 3-and 4-body cluster amplitudes. These amplitudes are in turn used to achieve a more appropriate decoupling of the full CC chain of equations than that leading to the standard CCSD equations. The RMR-CCSD method employs for this purpose a MR-CISD wave function obtained with a relatively small active or model space. To illustrate the capabilities of this approach, the computed potential energy curves for the HF, F 2 and H 2 O molecules are compared with the exact full CI or highly accurate large scale CI results, as well as with the MR-CISD results that are used as a source of 3-and 4-body amplitudes in the RMR-CCSD method. In all cases, the RMR-CCSD energies are far better than the standard CCSD energies or MR-CISD energies obtained with the same active space. The paper clearly demonstrates that the RMR-CCSD method provides very accurate data, while requiring only a modest increase in the computational effort over that of the standard CCSD method.

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Energy Levels ofF2andF2+<

Cited by 16 publications

References 2 publications

Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Reduced Multireference Coupled-Cluster Method: Barrier Heights for Heavy Atom Transfer, Nucleophilic Substitution, Association, and Unimolecular Reactions

Reduced multireference couple cluster method. II. Application to potential energy surfaces of HF, F2, and H2O

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Energy Levels ofF2andF2+<

Cited by 16 publications

References 2 publications

Normal-Valent ClOnX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Normal-Valent ClOnX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Reduced Multireference Coupled-Cluster Method: Barrier Heights for Heavy Atom Transfer, Nucleophilic Substitution, Association, and Unimolecular Reactions

Reduced multireference couple cluster method. II. Application to potential energy surfaces of HF, F2, and H2O

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Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation

Normal-Valent ClO_nX Compounds for n = 2, 3 and X = Cl, H: An MCSCF Investigation