The Spartan Computational Methods. Spartan'06 provides a wide range of computational methods, addressing the needs of educators, bench chemists, and professional modelers. All methods are easily accessed via Spartan's seamless graphical interface.
   
Methods:
     
  Molecular Mechanics Molecular mechanics is presently the only practical method for calculations on very large molecules or for conformational searching on highly flexible molecules. MMFF94, in particular, has proven to be a reliable and fast tool for conformational analysis. There are no atom limits for molecular mechanics calculations.

Both the SYBYL and MMFF94 force fields are supported. SYBYL extends throughout the entire Periodic Table while MMFF94 has been specifically parameterized to reproduce geometries and conformations of organic molecules and biopolymers. Additionally, an MMFFaq option applies an aqueous solvent energy correction to energy data, of special utility in ranking conformers.
     
  Semi-Empirical
Molecular Orbital

Semi-empirical models are the simplest of the quantum chemical schemes, and are useful for equilibrium and transition-state structure calculations. PM3, in particular, has proven to be a reliable tool for geometry calculations on transition metal inorganic and organometallic compounds.

MNDO, AM1, RM1 and PM3 methods are supported. MNDO/d extensions for heavy main-group elements have been implemented and PM3 parameters for most transition metals are available.

The RM1 (Recife Model 1) reparameterization of AM1 is new in Spartan'06. In most cases RM1 yields superior results to both AM1 an PM3 (for organic molecules), comparisons to MNDO were not available at the time of Spartan'06 release.
     
  Hartree-Fock
Molecular Orbital		 Hartree-Fock models useful for predicting structure, energy and property calculations, in particular for organic molecules.

A variety of standard basis sets are supported: STO-3G, 3-21G, 6-31G*, 6-311G*, cc-pVDZ, cc-pVTZ and cc-pVQZ, with extensions including (d), (d,p), (2d), (2d,2p), (2df, 2dp), (3d, 3p), (3df, 3dp) and diffuse functions and/or additional polarization functions. Also supported are a variety of pseudopotentials for calculations on molecules incorporating heavy elements. Spartan allows for the import of additional basis sets, and for the construction of user-created basis sets. Additionally, a new dual basis set procedure is is available, allowing the approximation of basis set extension using perturbation theory (for improved precision and performance).