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## Re: [ESPResSo-users] Control Temperature in version 3.2

**From**: |
Axel Arnold |

**Subject**: |
Re: [ESPResSo-users] Control Temperature in version 3.2 |

**Date**: |
Tue, 14 May 2013 22:41:01 +0200 |

**User-agent**: |
Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130330 Thunderbird/17.0.5 |

On 05/14/2013 08:36 PM, Salvador H-V wrote:

`However, in my script I am not making assumptions about the number
``degrees of freedom.
`
I just obtain the system temperature with:
set temp [expr [analyze energy kinetic]/(0.5*$np)]

`Hmm, but that means you assume 1 DOF per particle, if np is the number
``of particles. That should give you a factor 3 too high temperature, 1.5
``would be correct for 3 DOFs. Or 3 with ROTATION on, but
``ROTATION_PER_PARTICLE off. And if you use RATTLE to constrain some
``distances, these constraints need to be subtract from the number of DOFs...
`

`What I found is that only when I turn off the Rotation,
``Rotational_Inertia, Rotation_Per_Particle and Virtual_Sites I get
`
puts "The degrees of freedom is [degrees_of_freedom] " = 3!

`Yes, that is since the other features require rotation, and
``degrees_of_freedom checks if any rotation-related feature is on.
`

`If I understand well, if some of the virtual_sites features are
``activated, then rotation feature is automatically activated, then
`
% [code_info]
invalid command name "ESPResSo-3.2.0

`{ Compilation status { FFTW } { CONSTRAINTS } { BOND_ANGLE_HARMONIC }
``{ GAUSSIAN } { COMFIXED } { HERTZIAN } { PARTIAL_PERIODIC } {
``LENNARD_JONES } { VIRTUAL_SITES_RELATIVE } { EXTERNAL_FORCES } {
``TABULATED } { ROTATION } { SOFT_SPHERE } { VIRTUAL_SITES_NO_VELOCITY }
``{ LENNARD_JONES_GENERIC } { BOND_VIRTUAL } }"
`% [degrees_of_freedom]
invalid command name "6"

`That is correct, since rotation is on, so the particles have 6 DOFs.
``However, if ROTATION_PER_PARTICLE is on, that is no longer necessarily
``true, but depends on the particle. Only for particles, that have
``rotational properties, the number of DOFs should be 6, but then, that
``cannot be reflected by degrees_of_freedom. Might be the best to just
``dump the function, since it cannot give meaningful results anymore.
`
Axel
--
JP Dr. Axel Arnold
ICP, Universität Stuttgart
Pfaffenwaldring 27
70569 Stuttgart, Germany
Email: address@hidden
Tel: +49 711 685 67609