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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@13494 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp 2015-06-26 17:33:25 +00:00
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18
doc/units.html
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@ -34,6 +34,24 @@ of an input script.
www.physics.nist.gov. For the definition of Kcal in real units,
LAMMPS uses the thermochemical calorie = 4.184 J.
</P>
<P>The choice you make for units simply sets some internal conversion
factors within LAMMPS. This means that any simulation you perform for
one choice of units can be duplicated with any other unit setting
LAMMPS supports. In this context "duplicate" means the particles will
have identical trajectories and all output generated by the simulation
will be identical. This will be the case for some number of timesteps
until round-off effects accumulate, since the conversion factors for
two different unit systems are not identical to infinite precision.
</P>
<P>To perform the same simulation in a different set of units you must
change all the unit-based input parameters in your input script and
other input files (data file, potential files, etc) correctly to the
new units. And you must correctly convert all output from the new
units to the old units when comparing to the original results. That
is often not simple to do.
</P>
<HR>
<P>For style <I>lj</I>, all quantities are unitless. Without loss of
generality, LAMMPS sets the fundamental quantities mass, sigma,
epsilon, and the Boltzmann constant = 1. The masses, distances,

18
doc/units.txt
View File

@ -31,6 +31,24 @@ For all units except {lj}, LAMMPS uses physical constants from
www.physics.nist.gov. For the definition of Kcal in real units,
LAMMPS uses the thermochemical calorie = 4.184 J.
The choice you make for units simply sets some internal conversion
factors within LAMMPS. This means that any simulation you perform for
one choice of units can be duplicated with any other unit setting
LAMMPS supports. In this context "duplicate" means the particles will
have identical trajectories and all output generated by the simulation
will be identical. This will be the case for some number of timesteps
until round-off effects accumulate, since the conversion factors for
two different unit systems are not identical to infinite precision.
To perform the same simulation in a different set of units you must
change all the unit-based input parameters in your input script and
other input files (data file, potential files, etc) correctly to the
new units. And you must correctly convert all output from the new
units to the old units when comparing to the original results. That
is often not simple to do.
:line
For style {lj}, all quantities are unitless. Without loss of
generality, LAMMPS sets the fundamental quantities mass, sigma,
epsilon, and the Boltzmann constant = 1. The masses, distances,