[lammps-users] question about fix_modify, tchain and pchain

Hi everyone,

I cannot understand what the terms 'thermostat displacement' and 'thermostat velocity' mean in the lammps documentation when referring to the fix-modify energy setting and the tchain and pchain (chain thermostat and barostat) keywords of the fix npt command. Are these symbols namely, 'eta' and 'omega', described in the literature somewhere? They appear to be symbolically the same as the correction terms in equations of motion introduced by Melchionna (implemented in previous versions of LAMMPS). However, there is no description of how exactly the thermostat displacement and velocity are to be interpreted or what the symbols mean.

thanks
Shreevant

Aidan can answer this - but the papers cited in the fix nvt doc
page have the details.

Steve

Shreevant,

What Steve said. We put quite a bit of effort in to the fix_nh.html doc
page, and it is consistent with the papers cited. However, as always, the
ultimate documentation is the code itself. eta and omega are vectors that
are *almost* identical to the scalar eta and 3-vector omega used in the
original fix npt (i.e. when tchain=1, pchain=0, and barostat style = aniso,
mtk = no).

Aidan

Thanks, Steve and Aidan.