RATTLE in version 2017!

Dear all,

I have employed RATTLE method to constrain the rigid bonds in water molecules and to count the number of freedom for generating initial velocities of atoms as:

you can see which changes were done to fix rattle by examining the
file history in the LAMMPS git repository:
https://github.com/lammps/lammps/commits/master/src/RIGID/fix_rattle.cpp

for more details, you should contact the author of this style.

please note, that the information you provide is very vague (including
the LAMMPS version, there were lots of released LAMMPS versions in
both 2015 and 2017).
please check out: http://lammps.sandia.gov/guidelines.html

axel.

Dear Axel,

Thank you so much for your quick response. Versions I have tested lammps-10Aug15 and lammps-31Mar17 (even the current one).

I suggest you confer with the author of RATTLE for LAMMPS. Peter is CCd

on this message.

Steve

Hello Hai,

I haven't been involved in any changes to fix rattle since 2015. It's
always possible that a bug was there already in the original code or
that it has been introduced at a later stage. However, given the limited
information you provided, I am not sure I understand the problem
regarding the velocity initialisation.

Could you prepare a minimal working example to demonstrate the issue for
the latest stable version of LAMMPS? If there is a problem with the
constraints or number of degrees of freedom for rattle compared to
shake, then you should see the problem already by just looking at a
single water molecule. For testing purposes, you can compile LAMMPS with
RATTLE_DEBUG set to 1 (see fix_rattle.cpp), as explained in the doc
pages, so that you get some diagnostic output about the accuracy of rattle.

With regard to your second point, what do you mean by 'one of them has
error'? What is the kind of error you are talking about? A crash? Again
it could be due to rattle, but if there was a problem with the
constraints (rattle) I would expect all of your simulations to fail and
not only one of them. It's not unreasonable to assume that this one
simulation crashes because of some other problem. However, if you can
provide a reproducible and reasonably simple example to demonstrate that
rattle fails while shake works, we can look into that.

Best wishes,

Peter

Dear all,

Thank you so much for your explainations and suggestions.

Here, I am sending you input script and input data that I have simulated. If I did with lammps-10Aug15, results are adequate as the temperature at t=0 is equal to the imposed one, see as followings:

config_lammps.data (262 KB)

NPT_Main_lammps.in (2.98 KB)

NPT_Prod_lammps.in (1.15 KB)