Average Local Ionization Energies as a Route to Intrinsic Atomic Electronegativities
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- 作者：Peter Politzer ; Zenaida Peralta-Inga Shields ; Felipe A. Bulat ; Jane S. Murray
- 刊名：Journal of Chemical Theory and Computation
- 出版年：2011
- 出版时间：February 8, 2011
- 年：2011
- 卷：7
- 期：2
- 页码：377-384
- 全文大小：317K
- 年卷期：v.7,no.2(February 8, 2011)
- ISSN：1549-9626
文摘
Historically, two important approaches to the concept of electronegativity have been in terms of: (a) an atom in a molecule (e.g., Pauling) and (b) the chemical potential. An approximate form of the latter is now widely used for this purpose, although it includes a number of deviations from chemical experience. More recently, Allen introduced an atomic electronegativity scale based upon the spectroscopic average ionization energies of the valence electrons. This has gained considerable acceptance. However it does not take into account the interpenetration of valence and low-lying subshells, and it also involves some ambiguity in enumerating d valence electrons. In this paper, we analyze and characterize a formulation of relative atomic electronegativities that is conceptually the same as Allen鈥檚 but avoids the aforementioned problems. It involves the property known as the average local ionization energy, I̅(r), defined as , where 蟻i(r) is the electronic density of the ith orbital, having energy 蔚i, and 蟻(r) is the total electronic density. I̅(r) is interpreted as the average energy required to remove an electron at the point r. When I̅(r) is averaged over the outer surfaces of atoms, taken to be the 0.001 au contours of their electronic densities, a chemically meaningful scale of relative atomic electronegativities is obtained. Since the summation giving I̅(r) is over all occupied orbitals, the issues of subshell interpenetration and enumeration of valence electrons do not arise. The procedure is purely computational, and all of the atoms are treated in the same straightforward manner. The results of several different Hartree鈭扚ock and density functional methods are compared and evaluated; those produced by the Perdew鈭払urke鈭扙rnzerhof functional are chemically the most realistic.