[gmx-users] CG energy minimization

[Mark Abraham]

Myunggi Yi wrote:
> Dear users,
> 
> I'd like to restraint the protein during the minimization.
> I've got the following message.

In GROMACS, restraints are different from constraints. Check out the 
manual for details.

> ERROR: can not do Conjugate Gradients with constraints

Your .top is defining some constraints, and if you'd checked out the 
manual, you'd have confirmed that GROMACS can't handle constraints with 
the CG algorithm.

> em.mdp file
> +++++++++++++++++++++
> cpp                      = cpp
> include                  =
> define                   = -DPOSRES
> define                   = -DFLEXIBLE
> 
> ; RUN CONTROL PARAMETERS
> integrator               = cg
> ; Start time and timestep in ps
> tinit                    = 0
> dt                       = 0.001
> nsteps                   = 250
> +++++++++++++++++++++
> 
> How can I do this?

Either don't use constraints or don't use CG.

Mark