Progressive Systematic Underestimation of Reaction Energies by the B3LYP Model as the Number of C−C Bonds Increases: Why Organic Chemists Should Use Multiple DFT Models for Calculations Involving Polycarbon Hydrocarbons

Abstract

[reaction: see text] Computational studies of three different reaction types involving hydrocarbons (homolytic C-C bond breaking of alkanes, progressive insertions of triplet methylene into C-H bonds of ethane, and [2+2] cyclizations of methyl-substituted alkenes to form polymethylcyclobutanes) show that the B3LYP model consistently underestimates the reaction energy, even when extremely large basis sets are employed. The error is systematic and cumulative, such that the reaction energies of reactions involving hydrocarbons with more than 4-6 C-C bonds are predicted quite poorly. Energies are underestimated for slightly and highly methyl-substituted cyclic and acyclic hydrocarbons, so the errors do not arise from structural issues such as steric repulsion or ring strain energy. We trace the error associated with the B3LYP approach to its consistent underestimation of the C-C bond energy. Other DFT models show this problem to lesser extents, while the MP2 method avoids it. As a consequence, we discourage the use of the B3LYP model for reaction energy calculations for organic compounds containing more than four carbon atoms. We advocate use of a collection of pure and hybrid DFT models (and ab initio models where possible) to provide computational "error bars".

Performance of the M062X density functional against the ISOL set of benchmark isomerization energies for large organic molecules

“…The M062X functional appears to offer comparable isomerization energy prediction performance to the best performing currently available dispersion corrected functionals against this benchmark dataset.The performance of various levels of quantum chemical methods for estimating the isomerization energies (∆ isom E) and enthalpies (∆ isom H) of organic compounds has been the focus of a number of investigations over the past several years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This attention is primarily driven by the poor performance of many popular density functionals -most notably the B3LYP functional -with regard to these types of intramolecular rearrangements.…”

Non Bonded Interactions in cylindrical capacitor of (m, n) @ (m’, n’) @ (m”, n”) Three Walled Nano Carbon Nanotubes

“…We investigated density functional theories with theory of van der Waals densities for modeling exchange-correlation senergies for the nanotubes [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . The double ζ-basis set including polarize orbitals was used for boron and nitrogens atoms while single ζ-basis setincluding polarize orbital was applied for the TWCNTs, respectively 53 .…”

“…For non-covalent interactions,the BLYP methods are unable for describing van der Waals [51][52][53] TWCNTs systems by medium-ranges interaction such as interaction between three tubes of TWCNTs. The B3LYP and some other functional are not suitable for illustrating the exchanges and correlations energies indistant medium-range non-bonded system obviously.…”

“…The B3LYP and some other functional are not suitable for illustrating the exchanges and correlations energies indistant medium-range non-bonded system obviously. In addition, some novel studies have exhibited that inaccuracies of the medium-ranges exchanges energies lead to asystematic error to predictof molecular properties [53][54][55][56][57][58] . Geometry optimization and electronic structures have been accomplished using the semi empirical methods such as CNDO, MINDO, and ZINDO which their approach are based on an semi empirical solution ab-initio and the Kohn-Sham equation 57 also.…”

A nano capacitor with graphene electrodes and Methane - (h-BN)insulator

“…The lack of ability of B3LYP and most other popular functional to correctly describe medium-range of exchange and correlation energy limits their applicability for distant non-bonded systems of two electrodes and dielectric thickness in a capacitor. Moreover, some recent studies have shown that inaccuracy for the medium-range exchange energies lead to large systematic errors in the prediction of molecular properties 136 . A monolayer of graphene was optimized and allowed to relax to its minimum energy structure.…”