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Geometry optimizations are possible by using numerical gradients obtained from extrapolated energies. Analytical energy gradients cannot be used.
The following possibilities exist:
1.) If OPTG directly follows the EXTRAPOLATE command, the extrapolated energy is optimized automatically (only variable settings may occur between EXTRAPOLATE and OPTG).
Examples:
Extrapolating the energy for the last command:
Extrapolating the energy computed in a procedure:
Note that this is not possible if EXTRAPOLATE gets the input energies from variables.
2.) Using a procedure for the extrapolation:
By default, variable ECBS is optimized, but other variables (e.g. ECBSD) can be specified using the VARIABLE option on the OPTG command.