Barrier heights can be calculated with increased accuracy by using `PM7-TS`.
The PM7-TS method was parameterized to reproduce high-level *ab-initio* barrier heights, given a
`PM7` reaction geometry and a transition state geometry.
(The reaction geometry is the geometry of the system before ascending the
activation barrier.)

For `PM7-TS` to work, the reaction geometry must be first
calculated using `PM7`. The transition state must also be located and
refined using `PM7`. To use `PM7-TS`, run one calculation using the
reaction geometry, and one calculation using the transition state geometry, then
the barrier height is obtained by subtracting the heat of formation of the
reaction geometry system from that of the transition state geometry system.