Alex Borgoo

Durham University, Angleterre

Mercredi 7 mars à 14h, bibliothèque LCT, tour 12-13, 4e étage

The homogeneity under density scaling of the exchange-correlation and non-interacting kinetic energy functionals of Kohn-Sham density functional theory is investigated. Paying attention to the integer discontinuity, results for atoms and small molecules are presented. For the exchange-correlation functional, effective homogeneities are highly system-dependent on either side of the integer discontinuity. By contrast, the average homogeneity associated with the potential that averages over the discontinuity is generally close to 4/3 when the discontinuity is computed using positive affinities for systems that do bind an excess electron and negative affinities for those that do not. The proximity to 4/3 becomes increasingly pronounced with increasing atomic number. Evaluating the discontinuity using a zero affinity in systems that do not bind an excess electron instead leads to effective homogeneities on the electron abundant side that are close to 4/3. For the non-interacting kinetic energy functional, the effective homogeneities are less system-dependent and the effect of the integer discontinuity is less pronounced. Average values are uniformly below 5/3.

The evaluation of a previously developed expression for negative electron affinities in Kohn-Sham density functional theory is revisited. Exploring the implications of the homogeneity properties of the PBE exchange-correlation functional, the orbital energies are shifted to improve estimated electron affinities and an optimal homogeneity is established.

[1] Effective homogeneity of the exchange-correlation and non-interacting kinetic energy functionals under density scaling

A. Borgoo, A.M. Teale, and D.J. Tozer, J. Chem. Phys. 136 (2012) 034101.

[2] Homogeneity considerations to improve negative affinity estimates

A. Borgoo, D.J. Tozer, in preparation