[lammps-users] friction factor

Hi everybody,

I want to define a specific friction factor for my simulation. In this case, I am using a Langevin thermostat for my system. As I studied, it is possible to define the friction factor (gamma) as it is related to the dumping factor in fix Langevin. In this case, I wanted to receive Lammps experts validation for using dumping factor as 1/gamma to define the friction factor.


In a fluidic context, the “gamma” in a Langevin equation indeed controls the strength of viscous drag induced on a spherical particles by an implicit solvent. You can compare the drag term to Stokes’s Law, and the strength of the thermal fluctuation term follows from the Fluctuation-Dissipation Theorem.

Without knowing much, much more about your system, it is impossible to say if the physical description I just gave is correct for your system. That is much easier to answer if you ask an expert in your particular scientific field – this could be either your supervisor, or the authors of a paper where a similar version of Langevin dynamics has been used to study a system similar to your system.