EXTRACV
This is part of the colvar module

Allow PLUMED to use collective variables computed in the MD engine.

This feature requires the MD engine to use special instructions to pass to PLUMED the value of some pre-computed collective variable. Check the documentation of the MD code to find out which collective variables can be computed and passed to PLUMED. These variables can then be accessed by name using the EXTRACV action.

Examples

This example takes the lambda variable pre-computed in GROMACS and apply to it a restraint to keep it close to the value 3.

Click on the labels of the actions for more information on what each action computes
tested on v2.7
l: EXTRACV 
NAME
compulsory keyword name of the CV as computed by the MD engine
=lambda RESTRAINT
ARG
the input for this action is the scalar output from one or more other actions.
=l
KAPPA
compulsory keyword ( default=0.0 ) specifies that the restraint is harmonic and what the values of the force constants on each of the variables are
=10
AT
compulsory keyword the position of the restraint
=3
Glossary of keywords and components
Compulsory keywords
NAME name of the CV as computed by the MD engine