Electronegativity: The density functional viewpoint

Parr, Robert G.; Donnelly, Robert A.; Levy, Mel; Palke, William E.

doi:10.1063/1.436185

Cited by 3,136 publications

(1,792 citation statements)

References 21 publications

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“…There are profound negative consequences for this dependence on N. The principle of electronegativity equalization 5,21 is violated. 20 The (m + 1)-electron reactivities of one species toward an electrophilic reactant are identical to the corresponding m-electron reactivities of that same species toward a nucleophilic reactant.…”

Section: All Quantities Such As µ η S F(r) S(r)mentioning

confidence: 99%

On the Foundations of Chemical Reactivity Theory

2007

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In formulating chemical-reactivity theory (CRT) so as to give it a deep foundation in density-functional theory (DFT), Parr, his collaborators, and subsequent workers have introduced reactivity indices as properties of isolated reactants, some of which are in apparent conflict with the underlying DFT. Indices which are first derivatives with respect to electron number are staircase functions of number, making electronegativity equalization problematic. Second derivative indices such as hardness vanish, putting hardness-based principles out of reach. By reformulating CRT within our partition theory, which provides an exact decomposition of a system into its component species, we resolve the conflict. We show that the reactivity of a species depends on its chemical context and define that context. We establish when electronegativity equalization holds and when it fails. We define a generalization of hardness, a hardness matrix containing the self-hardness of the individual species and the mutual hardnesses of the pairs of species of the system, and identify the physical origin of hardness. We introduce a corresponding generalization of the Fukui function as well as of the local and global softnesses and the softness kernel of the earlier formulation. We augment our previous formulation of the partition theory by introducing a model energy function and express the difference between the exact and the model forces on the nuclei in terms of the new reactivity indices. For simplicity, our presentation is limited to time-reversal invariant systems with vanishing spin density; it is straightforward to generalize the theory to finite spin density.

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Section: All Quantities Such As µ η S F(r) S(r)mentioning

confidence: 99%

On the Foundations of Chemical Reactivity Theory

2007

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“…The underlying theory, partition-theory (PT), was used to construct a formulation of chemical reactivity theory (CRT) [3] which, for the first time, is consistent with the underlying density-functional theory [8,9] and is richer in structure than the preexisting CRT [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…[8] (PPLB), allows for the existence of noninteger numbers of electrons on each part, necessary e.g. for the definitions of electronegativity [12] and hardness [13], key indices of chemical reactivity [3], and for incorporating covalent bonding between inequivalent parts.…”

Section: Introductionmentioning

confidence: 99%

Partition Theory: A Very Simple Illustration

2007

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We illustrate the main features of a recently proposed method based on ensemble density functional theory to divide rigorously a complex molecular system into its parts [M.H. Cohen and A. Wasserman, J. Phys. Chem. A 111, 2229 (2007)]. The illustrative system is an analog of the hydrogen molecule for which analytic expressions for the densities of the parts (hydrogen "atoms") are found along with the "reactivity potential" that enters the theory. While previous formulations of Chemical Reactivity Theory lead to zero, or undefined, values for the chemical hardness of the isolated parts, we demonstrate they can acquire a finite and positive hardness within the present formulation.

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“…It is important that ionization potential I, electron affinity A, electrophilicity index x, chemical potential l, electronegativity v, hardness g and softness S be put into a MO framework. Based on density functional descriptors global chemical reactivity descriptors of compounds such as hardness, chemical potential, softness, electro negativity and electrophilicity index as well as local reactivity has been defined [75][76][77]. Pauling introduced the concept of electronegativity as the power of an atom in a compound to attract electrons to it.…”

Section: Frontier Molecular Orbital Analysismentioning

confidence: 99%