Results of Perdew-Zunger self-interaction corrected (PZ-SIC) density functional theory calculations of the atomization energy of 35 molecules are compared to those of high-level quantum chemistry calculations. While the PBE functional, which is commonly used in calculations of condensed matter, is known to predict on average too high atomization energy (overbinding of the molecules), the application of PZ-SIC gives a large overcorrection and leads to significant underestimation of the atomization energy. The exchange enhancement factor that is optimal for the generalized gradient approximation within the Kohn-Sham (KS) approach may not be optimal for the self-interaction corrected functional. The PBEsol functional, where the exchange enhancement factor was optimized for solids, gives poor results for molecules in KS but turns out to work better than PBE in PZ-SIC calculations. The exchange enhancement is weaker in PBEsol and the functional is closer to the local density approximation. Furthermore, the drop in the exchange enhancement factor for increasing reduced gradient in the PW91 functional gives more accurate results than the plateaued enhancement in the PBE functional. A step towards an optimal exchange enhancement factor for a gradient dependent functional of the PZ-SIC form is taken by constructing an exchange enhancement factor that mimics PBEsol for small values of the reduced gradient, and PW91 for large values. The average atomization energy is then in closer agreement with the high-level quantum chemistry calculations, but the variance is still large, the F2 molecule being a notable outlier.
|Number of pages||7|
|Journal||Procedia Computer Science|
|Publication status||Published - 2015|
|Event||International Conference on Computational Science, ICCS 2002 - Amsterdam, Netherlands|
Duration: 21 Apr 2002 → 24 Apr 2002
Bibliographical noteFunding Information:
This work was funded by the Academy of Finland trough its Centres of Excellence Programme (2012–2017) under Project No. 251748, and through its FiDiPro Programme under Project No. 263294, as well as the Icelandic Science Fund. S.L. gratefully acknowledges funding from the Magnus Ernrooth Foundation.
© The Authors. Published by Elsevier B.V.
- Density functional theory
- Exchange-correlation functional
- Self-interaction correction