46.1.1 Options to select the wavefunction and energy to be optimized
By default, the last computed energy is optimized, and
all commands on which the last energy calculation depends are automatically executed.
For certain purposes, e.g., optimization of counter-poise corrected energies
or Davidson corrected energies, the following options can be
used to alter the default behaviour.
- Specifies a start command. In each geometry optimization step all input beginning
with command to the current OPTG is processed. This input must not include numerical gradient or
Hessian calculations. If numerical gradients are needed, these will be computed for the final energy (or specified variable)
by OPTG. It is assumed that these commands have been executed before entering the OPTG program.
- specifies a procedure to be executed in each geometry optimization step. This must
define a complete energy calculation (orbital optimization and correlation treatment), and must
not include numerical gradient of Hessian calculations (numerical gradients will be computed automatically for the
optimized energy or variable). However, the procedure can include the calculation of analytical
gradients, for instance for counter-poise corrected optimizations in which a linear combination of several
gradient calculations is needed.
- Optimize the value of variable varname. This implies numerical gradients.