dof in compute temp/com

Dear LAMMPS users and developers,

likely this question had already been asked, but I couldn't find
something specific in the mailing list archive, so please forgive me, if I'm asking again.

Maybe also I'm wrong with following consideration.

Compute temp/com is computing the temperature of a group after removing it's cm velocity. Shouldn't the used degrees of freedom be d=3 less then available dof in the group? I mean isn't one actually computing the temperature as if the total momentum of the group is conserved?
I couldn't find this in the code, thus the question.



It's a frame-of-reference issue. By subtracting the CoM velocity, you shift to a material frame, rather than a laboratory frame.

The temperature should be frame-independent, so if your CoM velocity is not zero, the maths will introduce an error.


I stand corrected!