SAR QSAR Environ Res. 2004 Feb;15(1):43-54
e-Quantum chemistry free resources.
Laboratoire de Physico- et Toxico-Chimie des Systèmes Naturels, UMR 5472 CNRS, Université de Bordeaux I, 351, Cours de la Libération, 33405 Talence Cedex, France. email@example.com
Among computational chemistry methods, quantum mechanics calculates geometries and electronic structures with accuracy especially for systems with electronic delocalization. The use of a multiconfigurational approach is able to treat highly degenerated states such as those occurring at the transition state in some chemical reactions. Moreover, an accurate description of potential energy surfaces can be obtained with the evaluation of the dynamic electron correlation effects by this approach. Molecular properties range from simple dipole moments, vibrational frequencies or IR intensities to frequency dependent hyperpolarizabilities. Quantum chemical calculations are thus an attractive source of molecular descriptors which can be used in QSAR/QSPR studies and which can express all electronic and geometric properties of molecules. A survey and a comparison of the performance of free e-resources for semi-empirical and ab initio calculations is provided.