[lammps-users] rigid body and NPT

Hi Lammps users,

I would like to use npt simulations for rigid-coil coploymers. I can
only find commands fix rigid, rigid/nve, rigid/nvt. I checked the
mailing list, and found relevant posts:

http://sourceforge.net/mailarchive/message.php?msg_id=33ea1b0a0911020711n6216037ek2d7160851a975b04%40mail.gmail.com
http://sourceforge.net/mailarchive/message.php?msg_id=33ea1b0a0909140717k1f06104ah93f6ce54cb5861dd%40mail.gmail.com

Steve, you have mentioned that you have run NPT simulations for a
system containing rigid bodies in the first link above. Could you
please tell me how you manage it? Thank you in advance.

All the best,

Dongsheng

Hi Lammps users,

I would like to use npt simulations for rigid-coil coploymers. I can
only find commands fix rigid, rigid/nve, rigid/nvt. I checked the
mailing list, and found relevant posts:

the papers describing the theory behind fix rigid/nvt and fix rigid/nve
also has a derivation for npt, but it has not yet been implemented.
feel free to give it a shot. :wink:

http://sourceforge.net/mailarchive/message.php?msg_id=33ea1b0a0911020711n6216037ek2d7160851a975b04%40mail.gmail.com
http://sourceforge.net/mailarchive/message.php?msg_id=33ea1b0a0909140717k1f06104ah93f6ce54cb5861dd%40mail.gmail.com

Steve, you have mentioned that you have run NPT simulations for a
system containing rigid bodies in the first link above. Could you
please tell me how you manage it? Thank you in advance.

i don't know what steve did, but if you read the documentation
it seems to me that you can use fix npt on a system with a mix
of rigid bodies and other particles and then integrate only the
non-rigid objects with fix npt in combination with the dilate partial
option.

cheers,
    axel.

Axel,

Thank you very much for your reply. I can understand that we can use
npt with dilate partial option for non-rigid particles. For rigid
body, we have to use fix rigid/nvt. I have read the manual for the
dilate partial option. Since a global pressure or stress tensor is
computed for all atoms (I guess it includes atoms in rigid bodies), I
bet it is OK to use fix rigid/nvt for rigid bodies.

Could you please tell which papers have described the theory behind
fix rigid/nvt and fix rigid/nve? Thanks.

All the best,

Dongsheng

Your analysis below is correct. The papers for the rigid/nve and rigid/nvt
are cited in the doc pages.
Tony Sheh and Trung Dac Nguyen, who developed these 2 recent
fixes, also worked on a rigid/npt one. They were waiting until
the recent new versoin of fix npt came out, to see if they
can be merged/aligned nicely. You can ask them about it if
you like. Seach the mail list for their emails.

Steve