From 8d1033f0d98245a7d00ca0b8704ac58f4cd06f85 Mon Sep 17 00:00:00 2001
From: sjplimp Syntax:
fix temp/csvr command
+fix temp/csld command
+
fix ID group-ID temp/csvr Tstart Tstop Tdamp seed
+fix ID group-ID temp/csld Tstart Tstop Tdamp seed
+
fix 1 all temp/csvr 300.0 300.0 100.0 54324+
fix 1 all temp/csld 100.0 300.0 10.0 123321 +
Description:
-Adjust the temperature with a CSVR thermostat (Bussi), which -updates the velocities to a linear combination of the current -velocities with a gaussian distribution at the desired temperature in -every timestep. +
Adjust the temperature with a canonical sampling thermostat that uses +global velocity rescaling with Hamiltonian dynamics (temp/csvr) +(Bussi1), or Langevin dynamics (temp/csld) (Bussi2). +In the case of temp/csvr the thermostat is similar to the empirical +Berendsen thermostat in temp/berendsen, but +chooses the actual scaling factor from a suitably chosen (gaussian) +distribution rather than having it determined from the time constant +directly. In the second case the velocities are updated to a linear +combination of the current velocities with a gaussian distribution +of velocities at the desired temperature. Both termostats are applied +in every timestep.
The thermostat is applied to only the translational degrees of freedom for the particles, which is an important consideration for finite-size particles which have rotational degrees of freedom are being -thermostatted with this fix. The translational degrees of freedom can +thermostatted with these fixes. The translational degrees of freedom can also have a bias velocity removed from them before thermostatting takes place; see the description below.
@@ -64,11 +77,11 @@ keywords for the simulation box parameters and timestep and elapsed time. Thus it is easy to specify a time-dependent temperature.IMPORTANT NOTE: Unlike the fix nvt command which -performs Nose/Hoover thermostatting AND time integration, this fix -does NOT perform time integration. It only modifies velocities to +performs Nose/Hoover thermostatting AND time integration, these fixes +do NOT perform time integration. They only modify velocities to effect thermostatting. Thus you must use a separate time integration fix, like fix nve to actually update the positions of -atoms using the modified velocities. Likewise, this fix should not +atoms using the modified velocities. Likewise, these fixes should not normally be used on atoms that also have their temperature controlled by another fix - e.g. by fix nvt or fix langevin commands. @@ -77,7 +90,7 @@ langevin commands. a discussion of different ways to compute temperature and perform thermostatting.
-This fix computes a temperature each timestep. To do this, the fix +
These fixes compute a temperature each timestep. To do this, the fix creates its own compute of style "temp", as if this command had been issued:
@@ -97,7 +110,7 @@ custom command using the appropriate compute-ID. It also means that changing attributes of thermo_temp will have no effect on this fix. -Like other fixes that perform thermostatting, this fix can be used +
Like other fixes that perform thermostatting, these fixes can be used with compute commands that calculate a temperature after removing a "bias" from the atom velocities. E.g. removing the center-of-mass velocity from a group of atoms or only calculating @@ -116,24 +129,37 @@ thermal degrees of freedom, and the bias is added back in.
Restart, fix_modify, output, run start/stop, minimize info:
-No information about this fix is written to binary restart
+ No information about these fixes are written to binary restart
files.
The fix_modify temp option is supported by this
-fix. You can use it to assign a temperature compute
-you have defined to this fix which will be used in its thermostatting
+ The fix_modify temp option is supported by these
+fixes. You can use it to assign a temperature compute
+you have defined to these fixes which will be used in its thermostatting
procedure, as described above. For consistency, the group used by
-this fix and by the compute should be the same.
+these fixes and by the compute should be the same.
This fix can ramp its target temperature over multiple runs, using the
-start and stop keywords of the run command. See the
+ These fixes can ramp its target temperature over multiple runs, using
+the start and stop keywords of the run command. See the
run command for details of how to do this.
This fix is not invoked during energy minimization.
+ These fixes are not invoked during energy minimization.
+ These fixes compute a global scalar which can be accessed by various
+output commands. The scalar is the
+cummulative energy change due to the fix. The scalar value
+calculated by this fix is "extensive".
Restrictions:
This fix is not compatible with fix shake.
+ These fixes are not compatible with fix shake.
+ The fix can be used with dynamic groups as defined by the
+group command. Likewise it can be used with groups to
+which atoms are added or deleted over time, e.g. a deposition
+simulation. However, the conservation properties of the thermostat
+and barostat are defined for systems with a static set of atoms. You
+may observe odd behavior if the atoms in a group vary dramatically
+over time or the atom count becomes very small.
Related commands:
(Bussi) Bussi and Parrinello, Phys. Rev. E (2007) +(Bussi1) Bussi, Donadio and Parrinello, J. Chem. Phys. 126, 014101(2007) + + +
(Bussi2) Bussi and Parrinello, Phys. Rev. E 75, 056707 (2007)