Thermochemistry from Semiempirical Molecular Orbital Theory

Semiempirical quantum-chemical methods are reviewed with regard to their role as computational tools in thermochemistry. The theoretical background and the conventions of the established methods arc outlined, particularly for MNDO, AMI, and PM3. The deviations between calculated and observed heats of formation are evaluated statistically for several large sets of test molecules to assess the performance of the established methods. The results are compared with those from ab initio and density functional approaches and from more recent semiempirical developments.