A semi-empirical density functional-based thermochemical (SEDFT) method is presentedwhich provides a reliable estimate of the enthalpy of formation while avoiding thecomputationally expensive calculation of a vibrational force field. The method allows forthe calculation of enthalpies of formation of binding sites of proteins when thesurrounding protein is treated with lower quality procedures, as is common in ONIOMand other QM/MM methods. The SEDFT method has been parameterized usingB3LYP/6-31G(d) procedures, a reliable and efficient combination of functional and basisset. When applied to molecules containing elements in the set (H, C, N, O, S), theSEDFT method yields accuracies comparable to higher order methods which require anadditional order of magnitude of computation time. Parameterization has been carriedout for 16 elements (H, Li, C, N, O, F, Na, Mg, P, S, Cl, K, Ca, Fe, Zn, Br). The resultsare excellent for molecules containing non-metal and halogen atoms for which adequateexperimental enthalpy of formation data are available. However, the SEDFT methodyields only approximate results for inorganic molecules containing metal elements. Theapplications and limitations of the SEDFT method are discussed.

Semi-empirical density functional-based thermochemical method for the efficient approximation of enthalpies of formation

240th National Meeting (2010)

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