I'm planning to study a chemical system involving radical reactions such as H· and OH· addition or abstraction. Could you please suggest suitable DFT methods and basis sets for studying radical reactions.
You may get a very good benchmark study in Acc. Chem. Res. 2008, 41, 157−167
M06-2X method probably better for this type of reactions. You should be careful about spin contamination.
Dear Professor, I have encountered the same issue while doing theoretical analysis for radical site selectivity. But I have got some solution to do theoretical calculations for radical site prediction. From my knowledge, you may proceed for Fukui functions calculation to get a clear solution. DFT functional with B3LYP method may support for your query I think so. For doing Fukui calculations you may aware of charge and multiplicities for all the three anion, cation and neutral NBO's.
(Highlight: Please optimise your compound using DFT/B3LYP/6-311G(d,p) level of basis set using Charge(-1) and Multiplicity (2) for predicting radical sites. After getting your optimised output, you pl. do the NBO calculations for all the three anion, cation and neutral system. )
For your clarity I have attached my research paper published in ChemistrySelect-Wiley to understand the Fukui functions protocol. If you have any query related to this issue, please ask me at any time.
Thank you :)
First, you shold test the dependence of the DFT functionals(B3LYP, CAMB3LYP, M06-2X, vB97X-D24) by using your chemical system. B3LYP is one of the most popular functionals in computational chemistry. The M06-2X functional is a hybrid functional applicable to relatively weak-bonded systems. CAMB3LYP and vB97X-D include the long-range corrections to accurately describe the non-Coulomb parts of the exchange functional. As a result of this test, it is assumed that M06-2X method is optimal for your chemical system without spin contamination. Next, the dependence on the basis set will be examined with the use of the M06-2X functional. In such a test, please choose a combination that is most suitable for a chemical system involving radical reactions without spin contamination.
Hi,
Density functional theory (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. Using this theory, the properties of a many-electron system can be determined by using functionals, i.e. functions of another function, which in this case is the spatially dependent electron density. Hence the name density functional theory comes from the use of functionals of the electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry.
DFT has been very popular for calculations in solid-state physics since the 1970s. However, DFT was not considered accurate enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange and correlation interactions. Computational costs are relatively low when compared to traditional methods, such as exchange only Hartree–Fock theory and its descendants that include electron correlation.
Despite recent improvements, there are still difficulties in using density functional theory to properly describe intermolecular interactions (of critical importance to understanding chemical reactions), especially van der Waals forces (dispersion); charge transfer excitations; transition states, global potential energy surfaces, dopant interactions and some other strongly correlated systems; and in calculations of the band gap and ferromagnetism in semiconductors. Its incomplete treatment of dispersion can adversely affect the accuracy of DFT in the treatment of systems which are dominated by dispersion (e.g. interacting noble gas atoms) or where dispersion competes significantly with other effects (e.g. in biomolecules). The development of new DFT methods designed to overcome this problem, by alterations to the functional or by the inclusion of additive terms, is a current research topic.
With my best wishes.
I am also think DFT functionals(B3LYP, CAMB3LYP, M06-2X, vB97X-D24) is the best.
Yuji Kohno Debasish Mandal can you provide benchmark studies relatin gto you answers? Thanks in advance
You may get a very good benchmark study in Acc. Chem. Res. 2008, 41, 157−167
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