



Methods: 




Molecular Mechanics 
Molecular mechanics is presently the only practical method for calculations
on very large molecules. MMFF94 has been specifically
parameterized to reproduce geometries and conformations of organic
molecules. 




SemiEmpirical
Molecular Orbital 
Semiempirical models are the simplest of the quantum chemical schemes,
and are useful for equilibrium and transitionstate structure calculations.
The semiempirical method included in the Student Physical Chemistry
Edition, PM3, has proven to be a reliable tool for geometry calculations
on transition metal inorganic and organometallic compounds. Semiempirical
models are applicable to molecules containing up to 75 atoms. PM3
parameters for most transition metals are now available. 




HartreeFock
Molecular Orbital 
HartreeFock models are ideal for structure, energy and property
calculations, in particular for organic molecules. They are applicable
to molecules containing up to 30 atoms. Three basis sets are included:
321G, 631G* and 6311+G**. 




Density Functional
Theory (B3LYP & EDF2) 
Density functional models typically provide results of a quality
comparable to conventional correlated models such as MP2, but with
a computational time only slightly greater than that of HartreeFock
models. As such, they are particularly useful for highquality structure,
energy and property calculations, including calculations on transitionmetal
inorganic and organometallic compounds. B3LYP models are supported
for 631G* and 6311+G* basis sets and for molecules containing up
to 30 atoms. 




MøllerPlesset (MP2) 
MP2 is perhaps the simplest model to take reasonable account of
electron correlation, and generally provides accurate descriptions
of equilibrium structure, conformation and energetics of a variety
of chemical reactions, including reactions where chemical bonds are
broken. MP2 is supported for 631G* and 6311+G** basis sets and for
molecules containing up to 20 atoms. 


