Manual:Geometry Optimization

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To perform a geometry optimization with octopus one should set the CalculationMode to go. octopus uses the minimization routines from the GSL, but up to now only the methods that use the gradient of the function are available. The method to be used should be set using the variable GOMethod.

The stopping criteria can be set with the variables GOTolerance and GOMinimumMove . Then minimization will be stopped when all forces on ions are smaller than GOTolerance or when all species coordinates change less than GOMinimumMove during on minimization step. If none of the previous criteria is matched after a number of minimization steps equal to GOMaxIter then the minimization will be stopped with an error message.

After each minimization step taken by the GSL algorithms octopus will write the current geometry to a file named go.XXXX.xyz (XXXX is the iteration number) in the directory geom. As an extra information, the title of the xyz file (second line) contains the total energy.

Note that octopus is not particularly efficient in performing geometry optimizations and many times, if the stopping criteria are two small, the GSL routines will return an error message stating that they were unable to improve the solution.

At the end of the run, if the minimization was successful, the minimized geometry will be written to a file named min.xyz in the working directory.