A Critique of Pauli Repulsions and Molecular Geometry

Bader, R. F. W.; Preston, Harry J. T.

doi:10.1139/v66-170

Cited by 28 publications

(15 citation statements)

References 8 publications

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“…The increase of nonbonded repulsion makes valence electrons feel less potential wells. [34,35] In the case of carbonates, electrons feel less the potential of the oxygen nuclei within CO 3 2-anions. The decrease of electron binding energy in O atoms increases oxygen polarizability.…”

Section: Kinetics Constraints On Crystal Growth Of Carbonate and Phosmentioning

confidence: 99%

Crystal Growth of Inorganic and Biomediated Carbonates and Phosphates

Navas¹,

Martín‐Algarra²,

Roman³

et al. 2013

Advanced Topics on Crystal Growth

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Section: Kinetics Constraints On Crystal Growth Of Carbonate and Phosmentioning

confidence: 99%

Crystal Growth of Inorganic and Biomediated Carbonates and Phosphates

Navas¹,

Martín‐Algarra²,

Roman³

et al. 2013

Advanced Topics on Crystal Growth

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“…The p,-like density along the internuclear axis is squashed by the presence of the M' core. This is most certainly due to Pauli exclusion forces as exemplified by the charge redistribution in two of the atoms (19). There is a large increase of density in front of the halogen nucleus which augments the absolute value of qATU.…”

Section: Interpretation Of Field Gradients Q' (R) Alkali Field Gradientmentioning

confidence: 99%

Electric Field Gradients in Alkali Halide Molecules

Laplante¹,

Bandrauk²

1974

Can. J. Chem.

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. Can. J. Chem. 52,2143Chem. 52, (1974. The electric field gradient q has been calculated from Hartree-Fock wavefunctions for the molecules LiF, LiCI, LiBr, NaF, NaCI, NaBr, KF, and KCI. It is found that o and TC electrons behave quite differently. Exchange distortions are of great importance for a proper understanding of o contributions to q. Polarizations of n electrons into the bonding region are also considerable. These effects are responsible for failures of classical models and are further discussed using calculated density difference diagrams. Chem. 52, 2143Chem. 52, (1974. Le present article rapporte les resultats de calculs ab irzitio du gradient de champ electrique y pour la strie de molecules ioniques-type LiF, LiCI, LiBr, NaF, NaCI, NaBr, K F et KCI. Ces gradients ont ete obtenus a I'aide de fonction d'onde de type Hartree-Fock. Ces rksultats demontrent clairement que les electrons o et TC se comportent d'une facon tres differente dans ces molecules. Les distorsions d'echange presentes se rtvelent aussi d'importance lnajeure pour une comprihension adequate de la contribution des electrons o a la valeur de q. La polarisation des electrons n dans la region de liaison est a~~s s i considerable. L'ensemble de ces effets s'avere donc responsable de la faillite des modeles classiques pour I'interpretation de q. La disc~~ssion est appuyee des diagrammes de difference de densite correspondants. IntroductisnThe theoretical interpretation of the electric field gradient q in a molecule is of interest as it is a direct measure of the charge distribution. This follows from the fact that the interaction e2qQ, called the quadrupole coupling constant, between a nuclear quadrupole moment Q and the field gradient q of a molecular charge distribution p, is a weak interaction such that first-order perturbation theory is adequate (1). Experimentally eZgQ is determined from various hyperfine structures in resonance experiments of the microwave type (l,2). The field gradient q is also an intrinsic part of the theoretical expression for the force constant of a diatomic molecule (3).In this article we examine various models used to interpret q in ionic molecules, in particular, the alkali halides. Considerable theoretical work (4) has been done using a simple model based on ions with polarizable charge distributions. The problem then becomes the perturbation of an ion with a nuclear quadrupole moment by the field of an external point charge. The expression for the field gradient of simple ions with closed-shells configurations appears as 'NRCC Postgraduate Fellow. where superscripts f indicate positive and negative ions correspondingly. The factor y,' represents the effect of the deformation of the closed shells of the ion by the external charge on the value of q. If the distorted electron distribution opposes the field gradient of the external charge, then ymi is positive and there is a skieldingeffect, while if the distorted distribution enhances the field gradient, then y , ' is negative and there is an antishieldin...

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“…We have previously pointed out that such a disposition of the charge increase on the bonded side of the 0 and N nuclei in H 2 0 and NH, molecules is the expected one, in terms of regions where charge must be accumulated to achieve electrostatic equilibrium (5). One can determine a spatial region in a polyatomic molecule, the binding region, in which the electron density binds all the nuclei simultaneously.…”

mentioning

confidence: 95%

“…The formation of the ammonia molecule exhibits the same type of reorganization with respect to the separated atoms as noted for the water molecule (or for NH or OH). A ApSA(y) map for an approximate density for NH, has been previously given (5). The principal charge increase occurs along the three-fold symmetry axis both on the bonded and nonbonded side of the nitrogen nucleus.…”

mentioning

confidence: 99%

Polarizations of atomic and molecular charge distributions

Bader¹,

Keaveny²,

Runtz³

1969

Can. J. Chem.

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It is shown that the dominant polarization of a molecular charge distribution in the region of a nucleus of an atom which employs p orbitals in its bonding (Be -> F, Mg -> C1) is quadrupolar in nature, and dipolar for an atom which employs s orbitals (H, He, Li, Na). That these polari~ations are of a fundamental nature is demonstrated by showing that they represent the primary response of a charge distribution to an electric field, whether it be internal o r external, static or dynamic.Canadian Journal of Chemistry, 47, 2308 (1969) The polarization of a molecular charge distribution measured relative to the charge densities of its constituent separated atoms is determined by a density difference distribution ApsA(r). Such a distribution is constructed by subtracting from the molecular distribution, one obtained from the overlap of the undistorted atomic densities, the atomic densities being centered at the same nuclear positions as in the molecule. An extensive investigation of such ApsA(r) distributions (1-4)' for diatomic molecules formed from atoms in the first two rows of the periodic table, has revealed that the component atomic densities exhibit one of two dominant polarizations 011 the formation of a chemical bond. The polarization of atoms which employ principally s orbitals in their bonding, e.g., H, He, Li, and Na, is dbolar in character. The ApsA(r) distributioil in the vicinity of such a nucleus shows that the change in the atomic charge density corresponds to a simple transfer of charge from one side of the nucleus to the other. This is exemplified by the Aps,(r) map in the region of the proton for the OH molecule ( Fig. l(a)). The redistributioil of charge found in the Aps,(r) distributions for Be -> F or Mg + C1 atoms is characterized by an increase in charge density along the bond axis on both the bonded and nonbonded sides of the nucleus, and in its removal from a torus-like region perpendicular to the bond axis at the position of the nucleus. Such a q~radrupolar polarization, i.e., charge increase along one axis and its removal from another perpendicular to it, results in a gross In this note we wish to point out that the dipolar, and in particular, the quadrupolar polarizations, are the dominant ones in the formation of polyatomic systems as well, and offer evidence that such polarizations represent the primary response of a charge distribution to an imposed field.Figure l(b) shows a ApsA(r) map for the water molecule in the plane of the nuclei3. The pattern of the charge rearrangement in the vicinity of the oxygen nucleus is quadrupolar, and dipolar in the region of each proton. In fact, there is a striking similarity between this ApsA(r) map and the map for the OH diatomic molecule. The principal increase in charge density again occurs along a single axis, the two-fold symmetry axis, and charge is again concentrated in both the binding and antibinding regions of the oxygen nucleus. As in the OH molecule, the charge decrease occurs in a belt perpendicular to the axis of charge increase at ...

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A Critique of Pauli Repulsions and Molecular Geometry

Cited by 28 publications

References 8 publications

Crystal Growth of Inorganic and Biomediated Carbonates and Phosphates

Crystal Growth of Inorganic and Biomediated Carbonates and Phosphates

Electric Field Gradients in Alkali Halide Molecules

Polarizations of atomic and molecular charge distributions

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