AM1
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2008-06-04T06:00:20Z
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'''AM1''', or '''Austin Model 1''', is a [[Computational Chemistry#Semi-empirical and empirical methods|semi-empirical]] method for the [[quantum chemistry|quantum]] calculation of molecular electronic structure in [[computational chemistry]]. It is based on the [[NDDO|Neglect of Differential Diatomic Overlap]] integral approximation. Specifically, it is a generalization of the [[MNDO|modified neglect of differential diatomic overlap approximation]]. Related methods are [[PM3 (chemistry)|PM3]] and the older [[MINDO]].
AM1 was developed by [[Michael J. S. Dewar|Michael Dewar]] and co-workers and published in [[1985]]. AM1 is an attempt to improve the [[MNDO]] model by reducing the repulsion of atoms at close separation distances. The atomic core-atomic core terms in the MNDO equations were modified through the addition of off-center attractive and repulsive [[Gaussian]] functions.
The complexity of the parameterization problem increased in AM1 as the number of parameters per atom increased from 7 in [[MNDO]] to 13-16 per atom in AM1.
The results of AM1 calculations are sometimes used as the starting points for parameterizations of forcefields in [[molecular modelling]].
AM1 is implemented in the [[MOPAC]], [[AMPAC]], [[GAUSSIAN]], [[GAMESS (US)]], [[PC GAMESS]] and [[GAMESS (UK)]] programs.
An extension of AM1 is [[SAM1|SemiChem Austin Model 1]] (SAM1), which is implemented in the [[AMPAC]] program and which explicitly treats d-orbitals.
A model for the AM1 calculation of lanthanide complexes, called [http://www.sparkle.pro.br Sparkle/AM1], was also introduced and is implemented in [http://openmopac.net/ MOPAC2007].
'''AM1''' has been recently reparameterized, leading to the new [http://www.rm1.sparkle.pro.br RM1], or '''Recife Model 1''', available in [http://openmopac.net/ MOPAC2007], [http://www.wavefun.com/products/windows/Spartan06/win_spartan_cm1.html/ Spartan'06], [http://www.hyper.com/ Hyperchem 8], etc.
==See also==
* [[Semi-empirical quantum chemistry method]]s
==References==
Dewar, M. J. S., Zoebisch, E. G., Healy, E. F. and Stewart, J. J. P., ''Journal of the American Chemical Society'', '''107''', 3902, (1985).
Dewar, M. J. S., Jie, C., Yu. J., ''Tetrahedron'', 49, 5003, (1993).
Freire, R. O., Rocha, G. B., Simas, A. M., ''Inorganic Chemistry'', ''44'', 3299 (2005).
Rocha, G. B., Freire, R. O., Simas, A. M., and Stewart J. J. P., ''Journal of Computational Chemistry'', ''27'', 1101 (2006).
{{cite book | author=Leach, Andrew R. | title= Molecular Modelling| publisher = Pearson Education Limited| year=2001 | id=0582382106 }}
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[[Category:Semiempirical quantum chemistry methods]]
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