[lammps-users] Bias for velocities and dof

Hello,

I have two questions:

what is a vbias (found in compute_temp_com and compute_temp_sphere)?

double vbias[3]; // stored velocity bias for one atom

Second:

If I use a script like (3d system, dipoles):

fix 1 all nve/sphere update dipole
fix 2 all temp/berendsen 0.5 0.5 1

compute erot all erotate/sphere

compute mytemp all temp/sphere
compute_modify mytemp extra 1000 # to reduce the dof by N

thermo_modify temp mytemp

How many degrees of freedom does the
"temperature->calculate_scalar"-Funktion use un the
"compute_temp_sphere.cpp", does the change in "mytemp" and the
"thermo_modify" affect it - I think it does not, but I am not sure.

Best
G. Rosenthal

(I am trying to modify the berendsen thermostat to deal also with angular
velocities)

Vbias is to store some component(s) of velocity
to subtract out before computing the thermal
temperature, like a drift velocity. Various compute
temp commands treat this in different ways.

How many degrees of freedom does the
"temperature->calculate_scalar"-Funktion use un the
"compute_temp_sphere.cpp", does the change in "mytemp" and the
"thermo_modify" affect it - I think it does not, but I am not sure.

yes, the extra N will subtract dof from whatever compute temp
you apply it to - why do you think that is not the case?

Steve