Documentation Question: Are Reduced Energy Units Per Mole?

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I’m running a series of DPD simulations (which uses reduced units) and part of what I’m looking at is the total system energy. The documentation left me a little confused as to whether the energy units you get from reduced units systems is per mole of atoms/beads like those in real units for energy and mass, or if its the energy of the entire system.

I then ran a couple simulations (boxes of the same bead type, with differing numbers of beads) to test it, since it seemed like a silly question to ask the forum. When I saw the energy of the box doesn’t change as a function of system size I thought that it was per mole and moved on. However, now that I’m doing data analysis and converting the results to real units, everything is off from what I would expect by a multiple of avagadro’s number.

Since I’m not positive what’s going on and I can’t move forward, I was hoping that someone can confirm if the energy units in reduced units is given per mole of beads or if its the total energy for the entire system?

Thanks!!

Jacob Majikes

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jacob,

I'm running a series of DPD simulations (which uses reduced units) and part
of what I'm looking at is the total system energy. The documentation left
me a little confused as to whether the energy units you get from reduced
units systems is per mole of atoms/beads like those in real units for energy
and mass, or if its the energy of the entire system.

when you use reduced units, the default of the "thermo" output,
is normalized by the number of atoms (not molecules) in the system.
i.e. it implies: thermo_modify norm yes
for all other unit settings the default is to not normalize the energies:

http://lammps.sandia.gov/doc/thermo_modify.html

cheers,
    axel.