forked from lijiext/lammps
79 lines
2.7 KiB
Plaintext
79 lines
2.7 KiB
Plaintext
"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 "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
|