Valency. I. A quantum chemical definition and properties

Gopinathan, M. S.; Jug, Karl

doi:10.1007/bf02394809

Cited by 224 publications

(60 citation statements)

References 9 publications

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“…The final expressions for the QVIS have a common feature of being quadratic forms in the CBO displacements (hence, their name). These expressions are analogous to the successful definition of the covalent index by Gopinathan and Jug [4], which is preserved in the present approach. The model and numerical UHF results presented elsewhere [ 11 seem to support the present difference approach [ 1,3] to the chemical valence concept; namely, the QVIs have been shown to generate the overall (of the molecule as a whole) valence indices of typical diatomics in general agreement with chemical values.…”

Section: Introductionmentioning

confidence: 53%

Quantum mechanical valence study of a bond‐breaking–bond‐forming process in triatomic systems

Nalewajski

Formosinho

Varandas

et al. 1994

Int J of Quantum Chemistry

103

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The recently introduced set of the quadratic, two-electron covalent and ionic valence indices is used to investigate the bond-breaking-bond-forming (BB-BF) process in an atom exchange reaction between H2 and X (X = H, F-I) as well as in the 0 2 -H system. Valence changes accompanying selected charge reorganizations are examined within the three-orbital model and valence diagrams for symmetric transition states (TSS) are given. The UHF valence data for Liz0 and C02 and the H-H-X, 0-0-H, and 0-H-0 (ABC) TSS (collinear and angular) are reported and compared to valence data in the separated fragments limits (SFL), AB and BC. The overall valence, v ( A B C ) , and the total (ionic plus covalent) diatomic valences, and v~c, are used as measures of the overall bond-order in a concerted BE-BF reaction, to test the postulate of the bond-energy-bond-order (BEBO) model. In collinear TSS of H2X, 7 / = -I , i.e., one bonding electron pair, is found to be roughly preserved, whereas in the angular H2X and in collinear 0-H-0 TSS, the effect of increased valence at the saddle-point is observed, relative to that of diatomic fragments (reactants or products). For the angular 0-0-H TS, a similar increase in I v ( A B C ) J relative to both 0 2 and OH s n s is detected; smaller changes relative to the 0 2 data are found in the collinear TS. This observation is in agreement with earlier predictions from the intersecting-state model. The relative diatomic valences, v: ; / v: F and %'$/-viF, are shown to conserve the overall relative bond multiplicity around 1 in both collinear and angular TSS of the H2-X systems. 0 1994 John Wiley & Sons, Inc. qo = {PEP (p} = qo.ff + qO'P. These reference occupations and the associated atodion electron populations, no = {I: 4:) (the summation is over all OAOS of atom A), define the respective occupatiodpopulation displacements: AqP = P -0 , P 9 q . ( 3 ) 0 An = nno, The explicit expressions for the QVIS are defined as follows [l]:Aq = qq , Aq" = qff -qo3",

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Section: Introductionmentioning

confidence: 53%

Quantum mechanical valence study of a bond‐breaking–bond‐forming process in triatomic systems

Nalewajski

Formosinho

Varandas

et al. 1994

Int J of Quantum Chemistry

103

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“…Average valency of carbon atom is the third descriptor which appeared in the MLR model. This descriptor is a local electronic descriptor obtained by computational chemistry methods and represent the average valency of carbon atoms in a molecule [45]. Molecule with higher value of AVC is more hydrophobe, therefore its tendency to micellar media increases, hence the mean effect of this descriptor has positive sign (5.670).…”

Section: Resultsmentioning

confidence: 99%

Prediction of micelle–water partition coefficient from the theoretical derived molecular descriptors

Fatemi

Karimian

2007

Journal of Colloid and Interface Science

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“…The bond orders analyses [39,40] of small molecules are listed in Table 5. The symbols (U 1 , O 2 etc.)…”

Section: Population Analysis and Frontier Orbitalsmentioning

confidence: 99%

Structures, spectroscopic and thermodynamic properties of U2On (n = 0 ∼ 2, 4) molecules: a density functional theory study

Li¹,

Niu²,

Gao³

et al. 2013

J Mol Model

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The equilibrium structures, spectroscopic and thermodynamic parameters [entropy (S), internal energy (E), heat capacity (C p)] of U₂, U₂O, U₂O₂ and U₂O₄ uranium oxide molecules were investigated systematically using density functional theory (DFT). Our computations indicated that the ground electronic state of U₂ is the septet state and the equilibrium bond length is 2.194 Å; the ground electronic state of U₂O and U₂O₂ were found to be X³Φ and X³Σ(g) with stable C(∞v) and D(∞h) linear structures, respectively. The bridge-bonded structure with D(2h) symmetry and X³B₁(g) state is the most stable configuration for the U₂O₄ molecule. Mulliken population analyses show that U atoms always lose electrons to become the donor and O atoms always obtain electrons as the acceptor. Molecular orbital analyses demonstrated that the frontier orbitals of the title molecules were contributed mostly by 5f atomic orbitals of U atoms. Vibrational frequencies analyses indicate that the maximum absorption peaks stem from the stretching mode of U-O bonds in U₂O, U₂O₂ and U₂O₄. In addition, thermodynamic data of U₂O(n) (n = 0 ∼ 4) molecules at elevated temperatures of 293.0 K to 393.0 K was predicted.

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Valency. I. A quantum chemical definition and properties

Cited by 224 publications

References 9 publications

Quantum mechanical valence study of a bond‐breaking–bond‐forming process in triatomic systems

Quantum mechanical valence study of a bond‐breaking–bond‐forming process in triatomic systems

Prediction of micelle–water partition coefficient from the theoretical derived molecular descriptors

Structures, spectroscopic and thermodynamic properties of U2On (n = 0 ∼ 2, 4) molecules: a density functional theory study

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