If you do calculate a temperature for the rigid bodies, the +
If you calculate a temperature for the rigid bodies, the degrees-of-freedom removed by each rigid body are accounted for in the temperature (and pressure) computation, but only if the temperature group includes the entire rigid body. Rigid bodies in 3d have 6 @@ -174,10 +174,12 @@ which only have 5. Rigid bodies in 2d have 3 degrees of freedom. Note that linear rigid bodies in 3d of three or more atoms also have 5 degrees of freedom instead of 6, but LAMMPS will not detect this. So you should use the compute_modify command to -subtract an additional degree of freedom per rigid body. You may also -wish to explicitly subtract additional degrees-of-freedom if you use -the force and torque keywords to eliminate certain motions of the -rigid body, as LAMMPS does not do this automatically. +subtract an additional degree of freedom per rigid body. A linear +rigid body means one consisting of point particles lying on a straight +line. You may also wish to explicitly subtract additional +degrees-of-freedom if you use the force and torque keywords to +eliminate certain motions of the rigid body, as LAMMPS does not do +this automatically.
The rigid body contribution to the pressure of the system (virial) is also accounted for by this fix. diff --git a/doc/fix_rigid.txt b/doc/fix_rigid.txt index 35f2462842..6f6c83a5d6 100644 --- a/doc/fix_rigid.txt +++ b/doc/fix_rigid.txt @@ -156,7 +156,7 @@ the non-rigid atoms that surround one or more rigid bodies (i.e. explicit solvent) by appropriate choice of groups in the compute and fix commands for temperature and thermostatting. -If you do calculate a temperature for the rigid bodies, the +If you calculate a temperature for the rigid bodies, the degrees-of-freedom removed by each rigid body are accounted for in the temperature (and pressure) computation, but only if the temperature group includes the entire rigid body. Rigid bodies in 3d have 6 @@ -165,10 +165,12 @@ which only have 5. Rigid bodies in 2d have 3 degrees of freedom. Note that linear rigid bodies in 3d of three or more atoms also have 5 degrees of freedom instead of 6, but LAMMPS will not detect this. So you should use the "compute_modify"_compute_modify.html command to -subtract an additional degree of freedom per rigid body. You may also -wish to explicitly subtract additional degrees-of-freedom if you use -the {force} and {torque} keywords to eliminate certain motions of the -rigid body, as LAMMPS does not do this automatically. +subtract an additional degree of freedom per rigid body. A linear +rigid body means one consisting of point particles lying on a straight +line. You may also wish to explicitly subtract additional +degrees-of-freedom if you use the {force} and {torque} keywords to +eliminate certain motions of the rigid body, as LAMMPS does not do +this automatically. The rigid body contribution to the pressure of the system (virial) is also accounted for by this fix.