lammps/doc/compute_ke_eff.txt

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compute ke/eff command :h3

[Syntax:]

compute ID group-ID ke/eff :pre

ID, group-ID are documented in "compute"_compute.html command
ke/eff = style name of this compute command :ul

[Examples:]

compute 1 all ke/eff :pre

[Description:]

Define a computation that calculates the kinetic energy of motion of a
group of eFF particles (nuclei and electrons), as modeled with the
"electronic force field"_pair_eff.html.

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.

There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the {ke} or {etotal}
keyword used in thermodynamic output, as specified by the
"thermo_style"_thermo_style.html 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 {ke} 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 "compute
temp_eff"_compute_temp_eff.html 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.

IMPRORTANT NOTE: The temperature in eFF models should be monitored via
the "compute temp/eff"_compute_temp_eff.html command, which can be
printed with thermodynamic output by using the
"thermo_modify"_thermo_modify.html command, as shown in the following
example:

compute         effTemp all temp/eff
thermo_style    custom step etotal pe ke temp press 
thermo_modify   temp effTemp :pre
 
See "compute temp/eff"_compute_temp_eff.html.

[Output info:]

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 "this section"_Section_howto.html#howto_15 for an overview
of LAMMPS output options.

The scalar value calculated by this compute is "extensive".  The
scalar value will be in energy "units"_units.html.

[Restrictions:]

This compute is part of the USER-EFF package.  It is only enabled if
LAMMPS was built with that package.  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.

[Related commands:] none

[Default:] none