[gmx-users] Error in Conjugate Gradient Minimization

[Mark Abraham]

Arneh Babakhani wrote:
> Hello,
> 
> *When trying to do CG minimization, I keep getting the following error:*
> 
> Converted 0 out of 0 CUBICBONDS to morse bonds for mol 8
> processing coordinates...
> double-checking input for internal consistency...
> ERROR: can not do Conjugate Gradients with constraints (12309)
> There were 3 warnings
> -------------------------------------------------------
> Program grompp, VERSION 3.3.1
> Source code file: grompp.c, line: 1109
> 
> Fatal error:
> There were 1 error(s) processing your input
> 
> *Does anyone know what's going on here?

Yes, like it says, you're trying to do CG with constraints. :-) If you 
search the mailing list archives you will see some discussion of some 
water model that breaks CG because of constraints that are not 
eliminated by "constraints = none" in the .mdp file. I can't comment on 
whether your morse bonds are a problem.

Mark