Re: [gmx-users] CG Lincs errors

2016-12-16 Thread Nash, Anthony
Hi Peter, Thanks for the reply, I know we spoke in length on this mater only just recently. Many thanks for that. I’ve taken the time step of collagen in vacu down to 0.0001 and I’ve dropped the temp down to 280. I hope, running over 16 cores for two days that this should relieve any tension in

Re: [gmx-users] CG Lincs errors

2016-12-16 Thread Peter Kroon
As a note to Alex (and the rest of the list), the coarse-grained Martini forcefield is usually run with timesteps between 20-40 fs. 15fs is already rather low. I do agree that longer equilibration at low timestep (5 or 10) might help. Alternatively, Do you think a semiisotropic pressure coupling m

Re: [gmx-users] CG Lincs errors

2016-12-15 Thread Nash, Anthony
Alex and Mark, thanks for the information. I’ll drop dt down, significantly, drop the temperature, and run it for a long time. Thanks for the ideas. Anthony On 15/12/2016 21:54, "gromacs.org_gmx-users-boun...@maillist.sys.kth.se on behalf of Alex" wrote: >Mark is right, no two ways about it.

Re: [gmx-users] CG Lincs errors

2016-12-15 Thread Alex
Mark is right, no two ways about it. For initial equilibration and assessing preexisting structural strains try vacuum, _much_ smaller timesteps and possibly low temperatures in vacuum, only then transfer to solvent, etc. Algorithmically, LINCS requires convergence and you already are using a prett

Re: [gmx-users] CG Lincs errors

2016-12-15 Thread Mark Abraham
Hi, If a simulation isn't stable with a small time step (as I think you are saying) then moving to a larger time step is guaranteed to make that worse. Try an even smaller time step, for a long time, and see what happens. Or take a subset of your protein and see what happens. Or simulate in vacuo

[gmx-users] CG Lincs errors

2016-12-15 Thread Nash, Anthony
Hi all, I¹m hoping for some help. I¹m very sorry, this is a bit of a long one. I¹ve been struggling for almost a month trying to run a CG representation of our all-atom model of a collagen protein (3 polypeptide chains in a protein). Our original AMBER all-atom model had been successful modelling