[lammps-users] drag term in fix NVT

Hello Everyone,

   The fix NVT is written in the following format as given in LAMMPS documentation:

    ID group-ID nvt Tstart Tstop Tdamp keyword value ...

    * ID, group-ID are documented in fix command
    * nvt = style name of this fix command
    * Tstart,Tstop = desired temperature at start/end of run
    * Tdamp = temperature damping parameter (time units)
    * zero or more keyword/value pairs may be appended to the args
    * keyword = drag

        drag value = drag factor added to thermostat (0.0 = no drag)

   The documentation says that drag term alters the Nose-Hoover equations but
does that change the dynamic (diffusion coefficient) and structural properties
(pair correlation function)of the system that I am simulated, i.e. will the
properties of a system (say 1000 LJ patricles at T = 1.0 in reduced units)
simulated in NVT ensemble be different if simulated with drag term compared to
simulation without drag term?

   If anyone is aware of any reference to drag term formulation, please let me know.


Gaurav Pranami

Graduate Student
Chemical Engineering Dept.
Iowa State University

The drag term is just something we added to prevent oscillations.
If you are near equilibrium I don't think it should affect
dynamic properties like diffusion or structural props like g(r).