hello

How can I substract center of mass velocity of group atoms from kinetic energy contribution in stress/atom computation?

hello

How can I substract center of mass velocity of group atoms from kinetic energy contribution in stress/atom computation?

There's no current way to do that. You can subtract it

from a global temp, e.g. compute temp/com.

Steve

thanks..

but

what about that way:

(don't check yet)

..

# compute com velocity (one dimensional)

compute vy all reduce/region verx ave vy

thermo_style custom c_vy

run 0

# subtract com velocity from atoms

variable v equal -c_vy

velocity verx set 0 v 0 sum yes units box

# compute without com velocity

compute p verx stress/atom

run 0

#return com velocity to atoms

variable v equal c_vy

velocity verx set 0 v 0 sum yes units box

...

There is a variable option for vcm() of a group.

I don't see how that helps compute stress/atom

calcalate a velocity-squared term with the

COM velocity subtracted out.

Steve

I substract c.o.m-velocity from system and for result system(equal first but without vcm speed) calculate stress/atom,

then i try back the speed of the system - but this is don't work - variable rewrite with new "wrong" velocity.

I'm not clear on what you are asking now.

I told you before that LAMMPS doesn't subtract

the COM velocity in compute stress/atom. I don't

think you can make it do this form the input script,

if would require changing the source code.

Steve