Editing Optimize (section)

== Global optimization ==
Global optimization can be done using the conf_search command from the PyMOL`s terminal:

<source lang="python">
conf_search [selection string [, forcefield string [, method string [, nsteps int [, conformers int [, lowest_confor int]]]]]]
</source>


Where:
* selection: The name of teh object that is going to be minimized. The default value is 'all'. Using the GUI the default value is the first uploaded object.
* forcefield: Choose the forcefield used to compute the Internal Energy, options available are GAFF, MMFF94s, MMFF94, UFF and Ghemical. 
* method: Choose the method used to find the global minimum. The methods available are:

Systematic: Systematically iterate through all possible conformers according to Open Babel’s torsion library. This approach guarantee to find the local minimum (according to the forcefield in use). This approach scales to the power of N, where N is the number of rotatable bonds, hence it is only applicable to molecules with very few rotatable bonds.

Random: Conformations are generated by randomly choosing from the allowed torsion angles.

Weighted: This method uses an iterative procedure to find a global minimum. As with the Random method, it randomly choses from the allowed torsion angles but the choice is re-weighted based on the energy of the generated conformer. For molecules with to many rotatable bonds, that are not suitable for for the ''systematic'', this method is generally the best option.

* nsteps: Number of iteration steps during the minimization.
* conformers: Total number of conformers to be analysed. This option is not available when using the ''systematic'' method because all possible conformers are analysed.
* lowest_conf: This options sets how many of the low-energy conformers are retrieved as the result of a conformational search. Conformers are ordered from low to high energy. This option is not available when using the ''systematic'' method because this method return only the lowest energy conformer.

In general, it is a good idea to minimize the initial conformation before doing a conformational search.