unit converting between real and metal for SPC/Fw water

Dear all,

I am having some trouble when I tried to convert the unit from real to metal for SPC/Fw water. I can get correct results using real unit, with the density of water of ~0.98 g/cm^3 at 300K. But when I changed to "metal", the volume, as well as the obtained density was wrong. Did I missed anything?

I tried to get some answers from the mailing list archives, but I didn't find what I need. So sorry for disturb. Hopefully anyone would give me some hints.

Attached please find input files for real/metal units.

Thanks a lot.

Nancy

lammps.in-metal (1.49 KB)

lammps.in-real (1.48 KB)

data.h2o (32.1 KB)

I am having some trouble when I tried to convert the unit from real to metal for SPC/Fw water. I can get correct results >using real unit, with the density of water of ~0.98 g/cm^3 at 300K. But when I changed to "metal", the volume, as well as >the obtained density was wrong. Did I missed anything?

Undoubtably you did. If you do the conversion correctly,
you can run exactly the same simluation in any of the LAMMPS
unit choices. To begin, I would compare the thermodynamic
output on step 0. Every single quantity should agree between
the 2 calculations to very high precision, if you have done
all the unit conversions correctly. Then take a timestep. The
outputs should again agree to high precision. Then you
can run as long as you like, and the only difference should
be divergence due to round-off issues.

Steve