2010-09-02 03:53:20 +08:00
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<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>
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<HR>
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<H3>compute ke/eff command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>compute ID group-ID ke/eff
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
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<LI>ke/eff = style name of this compute command
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>compute 1 all ke/eff
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Define a computation that calculates the kinetic energy of motion of a
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group of eFF particles (nuclei and electrons), as modeled with the
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<A HREF = "pair_eff.html">electronic force field</A>.
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</P>
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<P>The kinetic energy for each nucleus is computed as 1/2 m v^2 and the
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kinetic energy for each electron is computed as 1/2(me v^2 + 3/4 me
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s^2), where m corresponds to the nuclear mass, me to the electron
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mass, v to the translational velocity of each particle, and s to the
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radial velocity of the electron, respectively.
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</P>
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<P>There is a subtle difference between the quantity calculated by this
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compute and the kinetic energy calculated by the <I>ke</I> or <I>etotal</I>
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keyword used in thermodynamic output, as specified by the
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<A HREF = "thermo_style.html">thermo_style</A> command. For this compute, kinetic
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energy is "translational" and "radial" (only for electrons) kinetic
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energy, calculated by the simple formula above. For thermodynamic
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output, the <I>ke</I> keyword infers kinetic energy from the temperature of
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the system with 1/2 Kb T of energy for each degree of freedom. For
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the eFF temperature computation via the <A HREF = "compute_temp_eff.html">compute
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temp_eff</A> command, these are the same. But
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different computes that calculate temperature can subtract out
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different non-thermal components of velocity and/or include other
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degrees of freedom.
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</P>
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<P>IMPRORTANT NOTE: The temperature in eFF models should be monitored via
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the <A HREF = "compute_temp_eff.html">compute temp/eff</A> command, which can be
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printed with thermodynamic output by using the
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<A HREF = "thermo_modify.html">thermo_modify</A> command, as shown in the following
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example:
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</P>
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<PRE>compute effTemp all temp/eff
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thermo_style custom step etotal pe ke temp press
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thermo_modify temp effTemp
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</PRE>
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<P>See <A HREF = "compute_temp_eff.html">compute temp/eff</A>.
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</P>
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<P><B>Output info:</B>
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</P>
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<P>This compute calculates a global scalar (the KE). This value can be
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used by any command that uses a global scalar value from a compute as
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2011-08-26 01:01:01 +08:00
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input. See <A HREF = "Section_howto.html#howto_15">this section</A> for an overview
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of LAMMPS output options.
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2010-09-02 03:53:20 +08:00
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</P>
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<P>The scalar value calculated by this compute is "extensive". The
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scalar value will be in energy <A HREF = "units.html">units</A>.
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</P>
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<P><B>Restrictions:</B>
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</P>
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2011-08-27 02:53:00 +08:00
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<P>This compute is part of the USER-EFF package. It is only enabled if
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2011-08-26 00:46:23 +08:00
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
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2010-09-02 03:53:20 +08:00
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LAMMPS</A> section for more info.
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</P>
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<P><B>Related commands:</B> none
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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