Gradient corrected density functional theory electronic structure

The application of density functional theory (DFT) to the study of the structure and reactivity of some molecules with unpaired electrons (radicals) performed by our group is presented. The results describe the application of LSD, gradient corrected and hybrid DFT methods to several small molecules. On average the results are as good as highly-correlated post-Hartree-Fock methods, but still some problems remain to be solved... 

Density functional techniques that use plane waves as basis sets for the valence electrons and describe the atomic cores by pseudopotentials or other special techniques only became applicable to zeolites recently. This approach had already been standard in solid state physics for many years, but only recent advances in computer technology and pseudopotential theory made it possible to apply it to solids with unit cells as large as those of zeolites. Moreover, the computational efficiency of plane wave methods is coupled to the DPT approximation and the accuracy needed in chemistry is reached only with gradient-corrected functionals which emerged only in recent years. The striking advantage of plane wave basis sets is the very efficient analytical calculation of the forces on the nuclei (only Hellmann-Feynman terms contribute) which allows structure optimizations and makes even molecular dynamics (MD) runs possible by the Car-Parrinello method. This type of technique is expected to make a major contribution to zeolite chemistry over the next few years. 

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