Austin Model 1, or AM1, is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry.
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 results of AM1 calculations are sometimes used as the starting points for parameterizations of forcefields in molecular modelling.
An extension of AM1 is SemiChem Austin Model 1 (SAM1), which is implemented in the AMPAC program and which explicitly treats d-orbitals.