Homec4science
Diffusion lammps (lammm-devel) Browse

lammps/doc/src/compute_ke_eff.txt
39d713b5a307lammm-devel

Last Change
Raw File

compute_ke_eff.txt
View Options

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
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 "Section_howto 15"_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
c4science · Help