forked from lijiext/lammps
84 lines
3.1 KiB
HTML
84 lines
3.1 KiB
HTML
|
<HTML>
|
||
|
|
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
|
||
|
|
</CENTER>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<HR>
|
||
|
|
|
||
|
|
<H3>compute ke/eff command
|
||
|
|
</H3>
|
||
|
|
<P><B>Syntax:</B>
|
||
|
|
</P>
|
||
|
|
<PRE>compute ID group-ID ke/eff
|
||
|
|
</PRE>
|
||
|
|
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
|
||
|
|
<LI>ke/eff = style name of this compute command
|
||
|
|
</UL>
|
||
|
|
<P><B>Examples:</B>
|
||
|
|
</P>
|
||
|
|
<PRE>compute 1 all ke/eff
|
||
|
|
</PRE>
|
||
|
|
<P><B>Description:</B>
|
||
|
|
</P>
|
||
|
|
<P>Define a computation that calculates the kinetic energy of motion of a
|
||
|
|
group of eFF particles (nuclei and electrons), as modeled with the
|
||
|
|
<A HREF = "pair_eff.html">electronic force field</A>.
|
||
|
|
</P>
|
||
|
|
<P>The kinetic energy for each nucleus is computed as 1/2 m v^2 and the
|
||
|
|
kinetic energy for each electron is computed as 1/2(me v^2 + 3/4 me
|
||
|
|
s^2), where m corresponds to the nuclear mass, me to the electron
|
||
|
|
mass, v to the translational velocity of each particle, and s to the
|
||
|
|
radial velocity of the electron, respectively.
|
||
|
|
</P>
|
||
|
|
<P>There is a subtle difference between the quantity calculated by this
|
||
|
|
compute and the kinetic energy calculated by the <I>ke</I> or <I>etotal</I>
|
||
|
|
keyword used in thermodynamic output, as specified by the
|
||
|
|
<A HREF = "thermo_style.html">thermo_style</A> command. For this compute, kinetic
|
||
|
|
energy is "translational" and "radial" (only for electrons) kinetic
|
||
|
|
energy, calculated by the simple formula above. For thermodynamic
|
||
|
|
output, the <I>ke</I> keyword infers kinetic energy from the temperature of
|
||
|
|
the system with 1/2 Kb T of energy for each degree of freedom. For
|
||
|
|
the eFF temperature computation via the <A HREF = "compute_temp_eff.html">compute
|
||
|
|
temp_eff</A> command, these are the same. But
|
||
|
|
different computes that calculate temperature can subtract out
|
||
|
|
different non-thermal components of velocity and/or include other
|
||
|
|
degrees of freedom.
|
||
|
|
</P>
|
||
|
|
<P>IMPRORTANT NOTE: The temperature in eFF models should be monitored via
|
||
|
|
the <A HREF = "compute_temp_eff.html">compute temp/eff</A> command, which can be
|
||
|
|
printed with thermodynamic output by using the
|
||
|
|
<A HREF = "thermo_modify.html">thermo_modify</A> command, as shown in the following
|
||
|
|
example:
|
||
|
|
</P>
|
||
|
|
<PRE>compute effTemp all temp/eff
|
||
|
|
thermo_style custom step etotal pe ke temp press
|
||
|
|
thermo_modify temp effTemp
|
||
|
|
</PRE>
|
||
|
|
<P>See <A HREF = "compute_temp_eff.html">compute temp/eff</A>.
|
||
|
|
</P>
|
||
|
|
<P><B>Output info:</B>
|
||
|
|
</P>
|
||
|
|
<P>This compute calculates a global scalar (the KE). This value can be
|
||
|
|
used by any command that uses a global scalar value from a compute as
|
||
|
|
input. See <A HREF = "Section_howto.html#4_15">this section</A> for an overview of
|
||
|
|
LAMMPS output options.
|
||
|
|
</P>
|
||
|
|
<P>The scalar value calculated by this compute is "extensive". The
|
||
|
|
scalar value will be in energy <A HREF = "units.html">units</A>.
|
||
|
|
</P>
|
||
|
|
<P><B>Restrictions:</B>
|
||
|
|
</P>
|
||
|
|
<P>This compute is part of the "user-eff" package. It is only enabled if
|
||
|
|
LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
|
||
|
|
LAMMPS</A> section for more info.
|
||
|
|
</P>
|
||
|
|
<P><B>Related commands:</B> none
|
||
|
|
</P>
|
||
|
|
<P><B>Default:</B> none
|
||
|
|
</P>
|
||
|
|
</HTML>
|