MNDO

MNDO, or Modified Neglect of Diatomic Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Differential Diatomic Overlap integral approximation. Similarly, this method replaced the earlier MINDO method. It is part of the MOPAC program and was developed in the group of Michael Dewar. It is also part of the AMPAC, GAMESS (US), PC GAMESS, GAMESS (UK), Gaussian and CP2K programs.

Later, it was essentially replaced by two new methods, PM3 and AM1, which are similar but have different parameterisation methods.

The extension by W. Thiel's group, called MNDO/d, which adds d functions, is widely used for organometallic compounds. It is included in GAMESS (UK).

MNDOC, also from W. Thiel's group, explicitly adds correlation effects though second order perturbation theory with the parameters fitted to experiment from the correlated calculation. In this way, the method should give better results for systems where correlation is particularly important and different from that in the ground state molecules from the MNDO training set. This include excited states and transition states. However Cramer (see reference below) argues that "the model has not been compared to other NDDO models to the degree necessary to evaluate whether the formalism lives up to that potential.

References

MNDO

• Dewar, Michael J. S.; Thiel, Walter (1977). "Ground states of molecules. 38. The MNDO method. Approximations and parameters". Journal of the American Chemical Society 99 (15): 4899. doi:10.1021/ja00457a004. 

MNDO/d

• Thiel, Walter; Voityuk, Alexander A. (1996). "Extension of MNDO to d Orbitals:  Parameters and Results for the Second-Row Elements and for the Zinc Group". Journal of Physical Chemistry 100 (2): 616. doi:10.1021/jp952148o. 
• Thiel, Walter (1996). "Perspectives on Semiempirical Molecular Orbital Theory". Advances in Chemical Physics. Advances in Chemical Physics 93: 703. doi:10.1002/9780470141526.ch10. ISBN 978-0-470-14152-6. 

MNDOC

• Cramer, C. J. (2002). Essentials of Computational Chemistry. John Wiley. p. 135. 
• Thiel, Walter (1981). "The MNDOC method, a correlated version of the MNDO model". Journal of the American Chemical Society 103 (6): 1413. doi:10.1021/ja00396a021. 
• Thiel, Walter (1981). "MNDOC study of reactive intermediates and transition states". Journal of the American Chemical Society 103 (6): 1420. doi:10.1021/ja00396a022. 
• Schweig, Armin; Thiel, Walter (1981). "MNDOC study of excited states". Journal of the American Chemical Society 103 (6): 1425. doi:10.1021/ja00396a023.