[lammps-users] Questions?

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1

Dear Lammps:

1)When I want to calculate the radial distribution function of the polymer melts,but because the RDF is not computed for distances longer than the force cutoff,then if I want an RDF for larger distance,what measures in detail I should take?

2)The code “fix msd command” is to computer the mean-squared displacement of the group of atoms every N steps,then when I want to study the mean-squared displacement of the polymer density melt (averaging over all the chains rather than all the atoms),what should I do? Can you give me some advice?(The code "fix gyration command"has the same problem.)

Thank you very much!

2

If you want to compute somthing further away than the cutoff, LAMMPS
doesn't have the info to compute it. At least in parallel. So you're better
off computing it as a post-processing step. I.e. write your own code
to do it, reading a dump file.

Re msd: you could modify fix msd to do what you want or add your
own command. See the Section modify doc pages.

Steve