forked from lijiext/lammps
154 lines
6.3 KiB
Plaintext
Executable File
154 lines
6.3 KiB
Plaintext
Executable File
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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fix nvt/asphere command :h3
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fix nvt/asphere/omp command :h3
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[Syntax:]
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fix ID group-ID nvt/asphere keyword value ... :pre
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ID, group-ID are documented in "fix"_fix.html command
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nvt/asphere = style name of this fix command
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additional thermostat related keyword/value pairs from the "fix nvt"_fix_nh.html command can be appended :ul
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[Examples:]
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fix 1 all nvt/asphere temp 300.0 300.0 100.0
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fix 1 all nvt/asphere temp 300.0 300.0 100.0 drag 0.2 :pre
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[Description:]
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Perform constant NVT integration to update position, velocity,
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orientation, and angular velocity each timestep for aspherical or
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ellipsoidal particles in the group using a Nose/Hoover temperature
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thermostat. V is volume; T is temperature. This creates a system
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trajectory consistent with the canonical ensemble.
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This fix differs from the "fix nvt"_fix_nh.html command, which
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assumes point particles and only updates their position and velocity.
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The thermostat is applied to both the translational and rotational
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degrees of freedom for the aspherical particles, assuming a compute is
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used which calculates a temperature that includes the rotational
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degrees of freedom (see below). The translational degrees of freedom
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can also have a bias velocity removed from them before thermostatting
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takes place; see the description below.
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Additional parameters affecting the thermostat are specified by
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keywords and values documented with the "fix nvt"_fix_nh.html
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command. See, for example, discussion of the {temp} and {drag}
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keywords.
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This fix computes a temperature each timestep. To do this, the fix
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creates its own compute of style "temp/asphere", as if this command
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had been issued:
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compute fix-ID_temp group-ID temp/asphere :pre
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See the "compute temp/asphere"_compute_temp_asphere.html command for
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details. Note that the ID of the new compute is the fix-ID +
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underscore + "temp", and the group for the new compute is the same as
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the fix group.
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Note that this is NOT the compute used by thermodynamic output (see
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the "thermo_style"_thermo_style.html command) with ID = {thermo_temp}.
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This means you can change the attributes of this fix's temperature
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(e.g. its degrees-of-freedom) via the
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"compute_modify"_compute_modify.html command or print this temperature
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during thermodynamic output via the "thermo_style
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custom"_thermo_style.html command using the appropriate compute-ID.
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It also means that changing attributes of {thermo_temp} will have no
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effect on this fix.
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Like other fixes that perform thermostatting, this fix can be used
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with "compute commands"_compute.html that calculate a temperature
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after removing a "bias" from the atom velocities. E.g. removing the
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center-of-mass velocity from a group of atoms or only calculating
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temperature on the x-component of velocity or only calculating
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temperature for atoms in a geometric region. This is not done by
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default, but only if the "fix_modify"_fix_modify.html command is used
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to assign a temperature compute to this fix that includes such a bias
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term. See the doc pages for individual "compute
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commands"_compute.html to determine which ones include a bias. In
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this case, the thermostat works in the following manner: the current
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temperature is calculated taking the bias into account, bias is
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removed from each atom, thermostatting is performed on the remaining
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thermal degrees of freedom, and the bias is added back in.
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:line
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Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in "Section_accelerate"_Section_accelerate.html
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the "Making
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LAMMPS"_Section_start.html#start_3 section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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[Restart, fix_modify, output, run start/stop, minimize info:]
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This fix writes the state of the Nose/Hoover thermostat to "binary
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restart files"_restart.html. See the "read_restart"_read_restart.html
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command for info on how to re-specify a fix in an input script that
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reads a restart file, so that the operation of the fix continues in an
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uninterrupted fashion.
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The "fix_modify"_fix_modify.html {temp} option is supported by this
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fix. You can use it to assign a "compute"_compute.html you have
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defined to this fix which will be used in its thermostatting
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procedure.
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The "fix_modify"_fix_modify.html {energy} option is supported by this
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fix to add the energy change induced by Nose/Hoover thermostatting to
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the system's potential energy as part of "thermodynamic
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output"_thermo_style.html.
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This fix computes the same global scalar and global vector of
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quantities as does the "fix nvt"_fix_nh.html command.
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This fix can ramp its target temperature over multiple runs, using the
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{start} and {stop} keywords of the "run"_run.html command. See the
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"run"_run.html command for details of how to do this.
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This fix is not invoked during "energy minimization"_minimize.html.
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[Restrictions:]
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This fix is part of the ASPHERE package. It is only enabled if LAMMPS
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was built with that package. See the "Making
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LAMMPS"_Section_start.html#start_3 section for more info.
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This fix requires that atoms store torque and angular momementum and a
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quaternion as defined by the "atom_style ellipsoid"_atom_style.html
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command.
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All particles in the group must be finite-size. They cannot be point
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particles, but they can be aspherical or spherical as defined by their
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shape attribute.
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[Related commands:]
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"fix nvt"_fix_nh.html, "fix nve_asphere"_fix_nve_asphere.html, "fix
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npt_asphere"_fix_npt_asphere.html, "fix_modify"_fix_modify.html
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[Default:] none
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