Other Computational Methods Available for Tin

Although most computational studies of organotin systems employ ECPs, other methods can be used to describe tin. These methods include semi-empirical methods, all-electron relativistic methods, and hybrid energy methods, such as Morokuma s ONIOM method and hybrid quantum mechanical and molecular mechanics methods (QM/MM). 

The zero-order regular approximation (ZORA), a two-component form of the fully-relativistic Dirac equation, is currently used for organotin computational calculations using basis sets specifically designed for ZORA. It should be noted that while all-electron calculations, whether non-relativistic or relativistic, can be used for organotin systems, the 6-3IG Pople basis set is not available for tin and therefore, most all-electron calculations involving tin employ the smaller 3-21G basis set. 

Valence bond (VB) theory may be used as an alternative to molecular orbital (MO) theory for computational organotin studies. Most MO calculations of organotin systems use Gaussian, GAMESS, or Amsterdam density functional (ADE) program suites. A variety of VB methods exist, and although VB wavefunctions are more difficult to calculate, some VB methods can also be implemented in these programs.  

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