forked from lijiext/lammps
81 lines
2.8 KiB
Plaintext
Executable File
81 lines
2.8 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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compute temp/sphere command :h3
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[Syntax:]
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compute ID group-ID temp/sphere :pre
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ID, group-ID are documented in "compute"_compute.html command
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temp/sphere = style name of this compute command :ul
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[Examples:]
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compute 1 all temp/sphere
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compute myTemp mobile temp/sphere :pre
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[Description:]
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Define a computation that calculates the temperature of a group of
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spherical particles, including a contribution from both their
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translational and rotational kinetic energy. This differs from the
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usual "compute temp"_compute_temp.html command, which assumes point
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particles with only translational kinetic energy.
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For 3d spherical particles, each has 6 degrees of freedom (3
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translational, 3 rotational). For 2d spherical particles, each has 3
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degrees of freedom (2 translational, 1 rotational).
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The rotational kinetic energy is computed as 1/2 I w^2, where I is the
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moment of inertia for a sphere and w is the particle's angular
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velocity.
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IMPORTANT NOTE: Fo "2d models"_dimension.html, particles are treated
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as spheres, not disks, meaning their moment of inertia will be the
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same as in 3d.
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A 6-component kinetic energy tensor is also calculated by this
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compute. The formula for the components of the tensor is the same as
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the above formula, except that v^2 and w^2 are replaced by vx*vy and
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wx*wy for the xy component.
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The number of atoms contributing to the temperature is assumed to be
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constant for the duration of the run; use the {dynamic} option of the
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"compute_modify"_compute_modify.html command if this is not the case.
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This compute subtracts out translational degrees-of-freedom due to
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fixes that constrain molecular motion, such as "fix
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shake"_fix_shake.html and "fix rigid"_fix_rigid.html. This means the
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temperature of groups of atoms that include these constraints will be
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computed correctly. If needed, the subtracted degrees-of-freedom can
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be altered using the {extra} option of the
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"compute_modify"_compute_modify.html command.
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[Output info:]
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The scalar value calculated by this compute is "intensive", meaning it
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is independent of the number of atoms in the simulation. The vector
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values are "extensive", meaning they scale with the number of atoms in
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the simulation.
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[Restrictions:]
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This compute requires that particles be represented as extended
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spheres and not point particles. This means they will have an angular
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velocity and a diameter which is determined either by the
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"shape"_shape.html command or by each particle being assigned an
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individual radius, e.g. for "atom_style granular"_atom_style.html.
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[Related commands:]
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"compute temp"_compute_temp.html, "compute
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temp/asphere"_compute_temp.html
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[Default:] none
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