Why B3LYP better is than M06-2X for HOMO-LUMO energy gap calculations?
Any references ?
Dear Özgür Alver,
I think the following is the paper you talk about. However, the authors do not state that B3LYP is better than M06-2X in calculating HOMO-LUMO gaps:
Journal of Spectroscopy
Volume 2016 (2016), Article ID 5396439, 15 pages
http://dx.doi.org/10.1155/2016/5396439
Research Article
Spectroscopic Investigations and DFT Calculations on 3-(Diacetylamino)-2-ethyl-3H-quinazolin-4-one
Yusuf Sert,1,2 Fatih Ucun,3 Gamal A. El-Hiti,4 Keith Smith,5 and Amany S. Hegazy5
1Department of Physics, Faculty of Art & Sciences, Bozok University, 66100 Yozgat, Turkey
2Sorgun Vocational School, Bozok University, 66100 Yozgat, Turkey
3Department of Physics, Faculty of Art & Sciences, Süleyman Demirel University, 32100 Isparta, Turkey
4Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia
5School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
Received 23 October 2015; Accepted 28 January 2016
Academic Editor: Christoph Krafft
Copyright © 2016 Yusuf Sert et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The theoretical and experimental vibrational frequencies of 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) were investigated. The experimental Laser-Raman spectrum (4000–100 cm−1) and FT-IR spectrum (4000–400 cm−1) of the newly synthesized compound were recorded in the solid phase. Both the theoretical vibrational frequencies and the optimized geometric parameters such as bond lengths and bond angles have for the first time been calculated using density functional theory (DFT/B3LYP and DFT/M06-2X) quantum chemical methods with the 6-311++G(d,p) basis set using Gaussian 03 software. The vibrational frequencies were assigned with the help of potential energy distribution (PED) analysis using VEDA 4 software. The calculated vibrational frequencies and the optimized geometric parameters were found to be in good agreement with the corresponding reported experimental data. Also, the energies of the lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital (HOMO), and other related molecular energies for 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) have been investigated using the same computational methods.
http://www.hindawi.com/journals/jspec/2016/5396439/
Hoping this will be helpful,
Rafik
Dear Ozgur,
You are looking for B3LYP and M06-2X, but I think it would be better if you think about a range-separated functional for calculating fundamental gap, like LC-wPBE.
Please look at J. Chem. Theory Comput, 2016, 12, 605
and J. Chem. Theory Comput. 2014, 10, 1035
Best wishes,
Sirous
It completely depends on the system you're investigating.
For example, on small gold nanoclusters, it was proved that GGA functionals outperform hybrids and range-separated hybrids.
http://pubs.acs.org/doi/abs/10.1021/jp411483x
Hi,
you could consider GW computations to get improved HOMO and LUMO levels.
See e.g.:
http://pubs.acs.org/doi/full/10.1021/acs.jctc.5b00453
Best,
Arnim
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