Semiempirical techniques MINDO/3 calculations

The semiempirical techniques available include EH, CNDO, INDO, MINDO/3, ZINDO, MNDO, AMI, and PM3. The ZINDO/S, MNDO/d, and PM3(TM) variations are also available. The semiempirical module seems to be rather robust in that it did well on some technically difficult test calculations. 

At least two semiempirical methods, MINDO/3 and MNDO, have been applied successfully to the study of linear polymers using conventional solid-state theoretical techniques. The MINDO/3 calculation, showed how the band-structure of polyethylene could be calculated, while in the MNDO calculation, the optimized geometry, electronic band structure, and vibrational frequencies for polyethylene were calculated. These calculation used conventional methods, which rely on the factorization of the infinite Hamiltonian into complex symmetry adapted functions, followed by the use of those functions in the construction of a real density matrix. A more general solid-state method has been developed, but like the other conventional methods, it is very slow, and these methods have not been used to any great extent. 

Calculations on the 4-aminobenzenediazonium ion were also carried out by Alcock et al. (1980a) using ab initio and MINDO/3 techniques. They came to the conclusion that both methods have poor predictive value for the geometry of an ion of such complexity. However, two other semiempirical methods, namely MNDO (Dewar and Thiel, 1977) and AM-1 (Dewar et al., 1985), were applied with better results to a similar, but even more complex, zwitterionic diazo compound, 2-diazonio-4,6-dinitrophenolate, by Lowe-Ma et al. (1988 see 4.4 in Sec. 4.2). 

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