dt_MD and dt_SRD

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1

Dear all;
I simulated a polymer (bead-spring chain) in a dilute solution by lammps
I used srd command to model solvent. now i have problem with dt_MD for positions and velocities updating of monomers of polymer and dt_srd that is interval time between collision steps.
I read in lammps documentation The SRD timestep dt_SRD is N times the step dt defined by the timestep command.
If a group of spherical particles,monomers of a chain, is taken into acount as a big-particle group in srd command, how are positions and velocities of monomers updeted?
If it is possible for you please help me?
Thanks in advance
Samira

2

In your script file you specify the time step (e.g. timestep 0.005) for your big particles in this case bead spring polymer. This time step is used for all your monomers. SRD particles are updated every N times timestep.

The answer to your question is no different from what the manual says and what is in srd/mix example.

3

I’m sorry, earlier I mistyped my answer.

  1. In your script file you specify the timestep (e.g. timestep 0.005) for your big particles in this case bead spring polymer. This time step is used for all your monomers.
  2. SRD particles use a time step of N* timestep.
  3. After every N steps the SRD particles velocity is reset.

My apologies again …