Calculations can be used to study TSs directly.
If the potential surface can be calculated (calculate energy for
any nuclear geometry), then TS structures on the surface can be found. Not limited to 2-/3-D.
So how do we find TS structures? - how to move on the potential
energy surface?
To find stable
structures: energy minimization.
Typically, a molecule may be built initially with a graphical building package, and the structure will not be perfect.
Several minimization methods have been developed.
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First-order methods use first derivatives of the energy
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Second-order methods use first and second derivatives