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41.
The nature of the chemical bonds in the diatomic molecules E2 (E=N–Bi, F–I), CO and BF has been studied with an energy partitioning analysis using gradient-corrected density functional theory calculations. The results make it possible to estimate quantitatively the strength of covalent and electrostatic attractions and the Pauli repulsion between the atoms. The data suggest that some traditional explanations regarding the strength of the molecules should be modified. The energy partitioning analysis shows that the chemical bonds in the group 15 diatomic molecules have significant electrostatic character, which increases from 30.1% in N2 to 58.3% in Bi2. The contribution of the electrostatic attraction to the binding interactions in Sb2 and Bi2 is larger than the covalent bonding. The strength of the bonding in the triply bonded dinitrogen is less than that of the bonding. The calculations indicate that E is between 32.2% (Bi2) and 40.0% (P2) of the total orbital interaction energy (Eorb). The much stronger bond of N2, as compared with the heavier group 15 E2 homologues, is not caused by a particularly strong contribution by the bonding, but rather by the relatively large interactions. The comparison of N2 with isoelectronic CO shows that the electrostatic character in the heteroatomic molecule is slightly smaller (28.8%) than in the homoatomic molecule. The contribution of the bonding in CO is larger (49.2%) than in N2 (34.3%). The reason why CO has a stronger bond than N2 is the significantly weaker Pauli repulsion in CO. The electrostatic character of the bonding in BF is slightly larger (32.0%) than in CO and N2. BF has much weaker -bonding contributions that provide only 11.2% of the covalent interactions, which is why BF has a much weaker bond than CO and N2. The chemical bonds in the dihalogen molecules have much higher covalent than electrostatic character. The Eorb term contributes between 74.4% (Br2) and 79.7% (F2) to the total attractive interactions. The relatively weak bond in F2 comes from the rather large Pauli repulsion.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
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Michael Koch Mahmood Saleem Gernot Krammer 《Particle & Particle Systems Characterization》2007,24(6):431-439
The measurement of a distributed property is frequently encountered in engineering applications. The impact of a possible measurement error on the measured distribution is described and two methods to account for such an error are detailed: A Fourier transform based deconvolution procedure and a moment based deconvolution approach via kernel estimators are presented. The deconvolution methods can be used in many particle characterization and process applications where particle features or properties are commonly presented in a distributed form. In the current instance, these methods are carefully explored by using artificially generated data and applied to experimental data obtained from filter cake thickness measurements. 相似文献
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We resume former discussions of the question, whether the spin–spin repulsion and the gravitational attraction of two aligned
black holes can balance each other. To answer the question we formulate a boundary value problem for two separate (Killing-)
horizons and apply the inverse (scattering) method to solve it. Making use of results of Manko, Ruiz and Sanabria-Gómez and
a novel black hole criterion, we prove the non-existence of the equilibrium situation in question. 相似文献
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