[gmx-developers] Position Restraints in Thermodynamic Integration

Carruthers, James j.carruthers2 at lancaster.ac.uk
Wed Sep 27 18:11:30 CEST 2017


I just tried it at 0.0, 0.5 and 1.0 restraint lambdas. Position restraints are fully applied in all states and DH/Dlambda is effectively zero when the foreign lambdas only have different restraint-lambdas.

From: gromacs.org_gmx-developers-bounces at maillist.sys.kth.se [gromacs.org_gmx-developers-bounces at maillist.sys.kth.se] on behalf of Berk Hess [hess at kth.se]
Sent: 27 September 2017 13:59
To: gmx-developers at gromacs.org
Subject: Re: [gmx-developers] Position Restraints in Thermodynamic      Integration


Looking at the code position restraints are controlled through the
restraint lambda. Have you actually tried it?
This does mean the manual needs to be updated.



On 27/09/17 14:46 , Carruthers, James wrote:
> Hello,
> In the online user guide for 2016.4 it states in mdp options that the restraint-lambdas directive only controls dihedral and pull code restraints. However, the 2016.4 manual states that position restraints can be interpolated for free energy calculations (pp. 137,138). I would like to be able to control position restraints as this will enable a convenient way to implement the Einstein crystal method of calculating solid state chemical potentials. This raises two questions, is there a technical reason why restraint-lambdas is restricted to controlling only those two parameters and is there a way to implement scaling position restraints outside of the *-lambdas framework that can be analysed by gmx bar?
> Best regards,
> James

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