AMSOL is a semiempirical quantum chemistry program that includes the MINDO/3, MNDO, AM1, and PM3 gas-phase Hamiltonians, the CM1A, CM1P, CM2/AM1, CM2/PM3, CM3/AM1, and CM3/PM3 charge models for calculating partial atomic charges, the SM1 - SM5.42R solvation models for calculating free energies of solvation in water, the SM4 solvation model for calculating free energies of solvation in alkanes, and the SM5.42R, SM5.4, SM5.2R, and SM5.0R solvation models for calculating free energies of solvation in any organic solvent. Most of the solvation models are based on the AM1 and/or PM3 Hamiltonians; the SM5.2R model is also available with the MNDO Hamiltonian. AMSOL can also accept user-specified specific reaction parameters. All solvation models that are denoted with an "R" in their name are for rigid-solute calculations and were designed to utilize accurate gas-phase geometries to predict solvation free energies. For all other models, geometry optimization is possible in both the gas phase and solution. For SM5.4 models analytic derivatives are available for geometry optimization.

In the SMx solvation models (with the exception of SM5.0R) solvation effects are included via two terms. The first accounts for electrostatic polarization of the solvent by the generalized Born approximation based on a distributed monopole representation of the solute charges with dielectric screening. Solute polarization is also included self-consistently. The second term is proportional to the solvent-accessible surface area, with a set of proportionality constants (surface tensions) which depend on the local nature of the solute for each atom's or group's interface with the solvent. The SM5.0R model contains no explicit representation of the electrostatics and the predicted solvation free energies are dependent only upon solute geometry.

Upon request, AMSOL can calculate Charge Model 1 (CM1), Charge Model 2 (CM2), or Charge Model 3 (CM3) partial charges. These charges are class IV charges that result from a semiempirical mapping of charges obtained by a population analysis into new charges that more accurately reproduce experimental gas-phase dipole moments and high-level ab initio partial charges fitted to electrostatic potentials. This version of AMSOL contains CM1, CM2, and CM3 parameterizations for the AM1 and PM3 Hamiltonians.