Towards an Optimal Gradient-dependent Energy Functional of the PZ-SIC Form

Journal Article · Mon Jun 01 00:00:00 EDT 2015 · Procedia Computer Science

DOI:https://doi.org/10.1016/j.procs.2015.05.417· OSTI ID:1208605

Jónsson, Elvar Örn ^[1]; Lehtola, Susi ^[2]; Jónsson, Hannes ^[3]

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1. Aalto Univ., Espoo (Finland). Dept. of Applied Physics
2. Aalto Univ., Espoo (Finland). Dept. of Applied Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Aalto Univ., Espoo (Finland). Dept. of Applied Physics; Univ. of Iceland, Reykjavik (Iceland). Faculty of Physical Sciences

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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1208605
• Journal Information: Procedia Computer Science, Vol. 51, Issue C; ISSN 1877-0509
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
density functional theory
self-interaction correction
exchange-correlation functional