Acta Phys. -Chim. Sin. ›› 2018, Vol. 34 ›› Issue (6): 675-682.doi: 10.3866/PKU.WHXB201801021

Special Issue: Special issue for Chemical Concepts from Density Functional Theory

• ARTICLE • Previous Articles     Next Articles

Multiply Charged Anions, Maximum Charge Acceptance, and Higher Electron Affinities of Molecules, Superatoms, and Clusters

László VON SZENTPÁLY*()   

  • Received:2017-10-30 Published:2018-03-20
  • Contact: László VON SZENTPÁLY


The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs XQ-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E(N, vex), is a continuous function of the average electron number, N, and the external potential, vex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E(N, vex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Qmax, and the higher electron affinities, AQ, as simple functions of the first electron affinity, A1, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Qmax, calc = 1 + 12A1/7(I -A1). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Qmax, GS = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A1/(I -A1). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF3), super-alkali species (OLi3), and neutral or charged transition-metal complexes, ABmLn0/+/-. The calculated second electron affinity A2, calc = A1-(7/12)(I -A1) is linearly correlated to the literature references A2, lit with a correlation coefficient R = 0.998. A2 or A3 values are predicted for further 24 species. The appearance sizes, nap3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.

Key words: Multiply charged negative ions, Their appearance sizes, Second electron affinity, Third electron affinity, Conceptual density-functional theory, Valence-state parabola model of electronegativity