[gmx-users] How to control the temperature when using an electric field?

David van der Spoel spoel at xray.bmc.uu.se
Sat Apr 23 09:40:33 CEST 2011

On 2011-04-23 09.38, Apoorv Kalyankar wrote:
> In GROMACS, I believe that whenever an external force is applied, the
> mean velocity of the group is subtracted before rescaling the
> velocities and then the mean velocity is added back in. So if you are
> expecting  a plug like flow then there should not be any problem. In
> other cases also, it should not create a problem since your external
> electric field is not that large.
This is correct for the acceleration option, but not for the electric 
field. Hence the E-field will introduce friction that will heat up the 

> And yes you should not remove the center of mass motion of the
> molecules otherwise you will get zero velocity.
> Apoorv
> On Fri, Apr 22, 2011 at 2:09 AM, lammps lammps<lammp2forum at gmail.com>  wrote:
>> Hi,
>> I want to use the option of E_x = 1   0.01  0 to add an electric field to
>> the simulated system in NVT ensemble.
>> Because there should exist an no zero velocity of center-of-mass in the x
>> direction. It seems that it is wrong to directly use the nose-hoover to
>> control the temperature.
>> it is also not reasonable to use nstcomm   = 1, because the velocity of
>> center-of mass in the x-axis should be kept when runing.
>> So, How to control the temperature? When calcating the temperature in the
>> process of simulations, how to exclude the velocity of center-of-mass of x
>> direction for controling the right T?
>> Thanks in advance.
>> --
>> wade
>> --
>> gmx-users mailing list    gmx-users at gromacs.org
>> http://lists.gromacs.org/mailman/listinfo/gmx-users
>> Please search the archive at
>> http://www.gromacs.org/Support/Mailing_Lists/Search before posting!
>> Please don't post (un)subscribe requests to the list. Use the
>> www interface or send it to gmx-users-request at gromacs.org.
>> Can't post? Read http://www.gromacs.org/Support/Mailing_Lists

David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se

More information about the gromacs.org_gmx-users mailing list