Nithin,

I am trying to use Tersoff potential for a simulation. The documentation

for Tersoff in the LAMMPS manual (manual dated 22 Jan, 2008) says that it

doesnt support stress/atom, energy/atom calculations. (pg 427) while at

the same time, the restrictions section in the documentation for compute

stress/atom command (pg 147) lists only airebo, meam and TIP4P as styles

which doesnt support it.

Is there an inconsistency? Can any one clarify?

Please see the 23 Jan 2008 bug fix:

"Updated the doc pages for the various pair styles to reflect that all

of them can now tally per-atom energy and stress so that they can be

used with the compute pe/atom and compute stress/atom commands."

http://lammps.sandia.gov/bug.html

Also, i am a bit confused about the units. I am using metal style units

in my simulation. Can anyone confirm the unit of the numbers computed

using compute stress/atom command. As far as i understand it should be in

eV for metal style.

Please see:

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

especially:

"Note that as defined in the formula, per-atom stress is the negative

of the per-atom pressure tensor. It is also really a stress-volume

formulation, meaning the computed quantity is in units of

pressure-volume. It would need to be divided by a per-atom volume to

have units of stress (pressure), but an individual atom's volume is

not easy to compute in a deformed solid or a liquid. Thus, if the

diagonal components of the per-atom stress tensor are summed for all

atoms in the system and the sum is divided by 3V, where V is the

volume of the system, the result should be -P, where P is the total

pressure of the system. "

Also see:

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

specifically:

"For style metal, these are the units:

distance = Angstroms

time = picoseconds

mass = grams/mole

energy = eV

velocity = Angstroms/picosecond

force = eV/Angstrom

temperature = degrees K

pressure = bars

charge = multiple of electron charge (+1.0 is a proton)

dipole = charge*Angstroms

electric field = volts/Angstrom "

So pressure-volume units for style metal are bars*angs^3.

Paul