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The semi-empirical SCF-MO method
The following is a compilation of the ZDO-based SCF-MO procedures:
- CNDO: Complete Neglect of DifferentialOverlap (around 1965 by John Pople - with a spherical AO approximation)
- INDO: Intermediate Neglect of Differential Overlap
- NDDO: Neglect of Diatomic Differential Overlap
- MINDO / 3: Modified INDO (was developed around 1975 by Michael Dewar - with complex parameterization)
- ZINDO: Developed by M. Zerner to take into account 3d and 4d transition metals
- MNDO: Modified NDO (by Michael Dewar and Walter Thiel around 1977)
- AM1: Austin Model 1 (as a slight modification by Michael Dewar and AndrewHolder in 1986)
- PM3: Parametric Model 3 (developed by JimmyStewart in 1988)
- PM5: Parametric Model 5 (developed by JimmyStewart, included in MOPAC 2002)
While the original methods (CNDO, INDO, NDDO) only contain approximations for theoretical quantities, further parameters have been introduced in later methods in order to achieve a better agreement between calculated and experimental molecular data. All of the above methods neglect the inner electrons of the atoms (for example the electrons in the 1s shells of C, N, O and F atoms) and consider the 2s and 2p orbitals; these electrons are considered in the field of the atomic cores.