Austin Model 1, or AM1, is a
semi-empirical
Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences an ...
method for the
quantum calculation of molecular electronic structure in
computational chemistry. It is based on the
Neglect of Differential Diatomic Overlap integral approximation. Specifically, it is a generalization of the
modified neglect of differential diatomic overlap approximation.
Related methods are
PM3 and the older
MINDO
MINDO, or Modified Intermediate Neglect of Differential Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Intermediate Neglect of Differential Overlap ( ...
.
AM1 was developed by
Michael Dewar and co-workers and published in 1985. AM1 is an attempt to improve the
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 Diatomic Differential Overlap integral approximation. ...
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
Carl Friedrich Gauss (1777–1855) is the eponym of all of the topics listed below.
There are over 100 topics all named after this German mathematician and scientist, all in the fields of mathematics, physics, and astronomy. The English eponymo ...
functions.
The complexity of the parameterization problem increased in AM1 as the number of parameters per atom increased from 7 in
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 Diatomic Differential Overlap integral approximation. ...
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
Molecular modelling encompasses all methods, theoretical and computational, used to model or mimic the behaviour of molecules. The methods are used in the fields of computational chemistry, drug design, computational biology and materials sci ...
.
AM1 is implemented in the
MOPAC
MOPAC is a popular computer program used in computational chemistry. It is designed to implement Semi-empirical quantum chemistry method, semi-empirical quantum chemistry algorithms, and it runs on Windows, Mac, and Linux.
MOPAC2016 is the current ...
,
AMPAC AMPAC is a general-purpose semiempirical quantum chemistry program. It is marketed by Semichem, Inc. and was developed originally by Michael Dewar and his group.
The first version of AMPAC (2.1) was made available in 1985 through the Quantum Che ...
,
Gaussian
Carl Friedrich Gauss (1777–1855) is the eponym of all of the topics listed below.
There are over 100 topics all named after this German mathematician and scientist, all in the fields of mathematics, physics, and astronomy. The English eponymo ...
,
CP2K
CP2K is a freely available ( GPL) quantum chemistry and solid state physics program package, written in Fortran 2008, to perform atomistic simulations of solid state, liquid, molecular, periodic, material, crystal, and biological systems. It prov ...
,
GAMESS (US)
General Atomic and Molecular Electronic Structure System (GAMESS (US)) is computer software for computational chemistry program. The original code started on October 1, 1977 as a National Resources for Computations in Chemistry project. In 1981, t ...
,
PC GAMESS
Firefly, formerly named PC GAMESS, is an ab initio computational chemistry program for Intel-compatible x86, x86-64 processors based on GAMESS (US) sources. However, it has been mostly rewritten (60-70% of the code), especially in platform-spe ...
,
GAMESS (UK)
General Atomic and Molecular Electronic Structure System (GAMESS-UK) is a computer software program for computational chemistry. The original code split in 1981 into GAMESS-UK and GAMESS (US) variants, which now differ significantly. Many of the ...
, and
SPARTAN programs.
An extension of AM1 is
SemiChem Austin Model 1 (SAM1), which is implemented in the
AMPAC AMPAC is a general-purpose semiempirical quantum chemistry program. It is marketed by Semichem, Inc. and was developed originally by Michael Dewar and his group.
The first version of AMPAC (2.1) was made available in 1985 through the Quantum Che ...
program and which explicitly treats d-orbitals.
An extension of AM1 is
AM1* that is available in
software.
See also
*
Semi-empirical quantum chemistry method
Semi-empirical quantum chemistry methods are based on the Hartree–Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where ...
s
Notes
References
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*
Semiempirical quantum chemistry methods
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