there are no image files attached to this e-mail. …and those attached to the e-mail you sent me privately had no legend, no explanation of what is what. so those were pretty much useless, especially for somebody like me, that does not do research in the area of langevin or brownian dynamics.
furthermore, fix nve does not update time. that is done by the Verlet integrator class (or the r-RESPA class).
you have to provide more context. when i look through the mailing list archives, i also see, that you had some more extensive modifications already done several months ago. what happened to those?
axel.
I was not working on it for a long time. Now started it again . The modifications that i did was making my simulation crash after certain number of time steps. Got frustrated and moved on. Now giving it a second try.
In the pictures, r is the position, a dot(.) on top signifies derivative, U is the total pair wise interaction potential experienced by a particle (here lj interaction with cut_off), ei is a direction vector which is computed from the second equation, and Gammas are Gaussian white noise, T is temperature, and the rest are constants. On putting f = 0, the 1st equation is identical to the equation which governs the langevin thermostat.
https://lammps.sandia.gov/doc/fix_langevin.html
ei are some kind of direction cosines values, specific for each particles. Initially they are to be taken from the user like initial coordinates and velocities from the data file, then they should be first solved by using equation 2 (2.png) and then used in equation 1 (1.png) to update velocity and position.
Thanks,
Jeet
This formulation is overdamped (Brownian), whereas LAMMPS only uses a (non-)overdamped (Langevin) formulation. There is a pull request that adds a similar (but not over-damped) active force to LAMMPS here: https://github.com/lammps/lammps/pull/1178
This formulation is overdamped (Brownian), whereas LAMMPS only uses a (non-)overdamped (Langevin) formulation. There is a pull request that adds a similar (but not over-damped) active force to LAMMPS here: https://github.com/lammps/lammps/pull/1178
I was just about to mention this. I hope this gets approved and merged. It’s a cool feature.
Jeet, I suggest that you take a look at what this fix does before adding new code to LAMMPS. (The current version of the documentation is here.) If it does not do what you want, perhaps you could make modifications to this fix instead of submitting your own. (In particular if your’s is not working. I had to do this recently. I wrote a crude version of fix bond/react. In the end, we decided not to publish this code, but to add this functionality to fix bond/react. Doing this helps keep the number of fixes from proliferating too much.)