Per multisphere computations like per atom computations

Submitted by RonMexico on Tue, 09/28/2021 - 00:01

Does anyone know how per multisphere quantities can be manipulated like per atom quantities? For example, with a mixture of spheres, I could do the following computation if I would like to:

variable velx atom vx
variable vely atom vy
variable sqvel atom sqrt(v_velx^2+v_vely^2)
compute vel all reduce ave v_sqvel

How can I do something similar but where I am no longer concerned with individual atoms but individual multispheres? I can use compute multisphere to get properties of each multisphere, but there does not seem to be a way to work with those properties to compute other quantities as you can with the variable atom command. Is there a way that I am missing? I don't know how to get beyond

compute multivel all multisphere property vcm
compute multipos all multisphere property xcm

If I want to compute the average (or sum, etc.) of c_multivel[1]/c_multipos[1] there does not seem to be a way. Any ideas?

Thanks!

mschramm | Tue, 09/28/2021 - 15:46

Hello,
I don't believe there is a ready made command in LIGGGHTS that does this.
If it doesn't need to be computed while the simulation is running, than I recommend calculating this value after the fact using the output files.
If it does, than I would suggest the python wrapper or writing your own compute/reduce/mol command.