Molecular Structures of Covalently Bound Main Group Elements

1 Molecular Structures of Covalently Bound Main Group Elements 

Andzelm and Wimmer, 1992, published one of the first comprehensive studies on the performance of approximate density functional theory in which optimized molecular geometries were reported. These authors computed the geometries of several organic species containing the atoms C, N, O, H, and F at the local SVWN level, using a polarized double-zeta basis set optimized for LDA computations. Some trends have been discerned 

Gradient corrections have been introduced in order to correct for shortcomings of the LDA. Hence, with regard to what we have learned above, one can assume that their application should result in an expansion of those bond lengths that are underestimated at the LDA level, whereas too long bonds should be contracted. To put these simple-minded anticipations into practice, let us consider the bond lengths in the first two columns of Table 8-2. 

26 This set consists of 32 small neutral first-row species and although this is not a very representative testing ground for many chemical problems, it has become a de facto standard used by several other groups. We will refer to it as the 4 JGP set in die following discussions. 

Bond SVWNa BLYPa SVWNb BLYPb BP86b BPW91b Experiment 

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