Validation of the density-functional based tight-binding approximation method for the calculation of reaction energies and other data -: art. no. 114110

We investigated the performance of the approximative density. functional method DFTB versus BLYP and G2 with respect to zero-point corrected reaction energies, vibrational frequencies, and geometry parameters for a set of 28 reactions and 22 representative molecules containing C, H, N, and O (DFTB-density-functional based tight-binding approximation). The DFTB reaction energies show a mean absolute deviation versus the G2 reference of 4.3 kcal/mol only. The corresponding value for the vibrational frequencies amounts to 75 cm(-1) versus BLYP/cc-pVTZ. With very few exceptions bond lengths and angles are in excellent agreement with the results of higher-level methods. (c) 2005 American Institute of Physics.