velocity/tspin command

Syntax

velocity/tspin group-ID create T seed keyword value ...

• group-ID = ID of group of atoms whose spin velocities will be set

• create = style name of this command

• T = desired spin temperature (temperature units, K in metal units)

• seed = random number seed (positive integer)

• zero or more keyword/value pairs may be appended

• keyword = spinmass or mom

  spinmass value = ms
    ms = spin mass multiplier relative to atomic mass (adim)
  mom value = yes or no
    yes = remove net spin momentum for each atom type
    no = retain net spin momentum

Examples

fix 1 all nve/tspin
velocity/tspin all create 300.0 12345 spinmass 0.0075

Description

Added in version TBD.

Initialize auxiliary spin velocities for TSPIN at the specified temperature. Unlike the ordinary velocity command, this command does not modify atomic velocities. The temperature is defined by compute temp/tspin.

Spin velocities are generated from a Gaussian distribution and rescaled separately for each atom type to the specified temperature. With mom yes, the spin-mass-weighted mean velocity of each atom type is subtracted before rescaling, so that its total auxiliary spin momentum vanishes,

\[\sum_{i\in\mathrm{type}}m_{s,i}\vec{v}_i^s = 0.\]

The spinmass keyword sets each atom’s auxiliary spin mass to the specified multiple of its atomic mass. If omitted, previously assigned spin masses are used. When spinmass is also specified in a TSPIN integrator, the integrator overrides these values at the start of each run.

Restrictions

This command requires atom_style spin and the SPIN package; see Build package. The simulation box, atoms, and a TSPIN integrator must be defined before using this command.

Related commands

velocity, fix nve/tspin, fix nvt/tspin, compute temp/tspin

Default

The default is mom yes. Without spinmass, existing spin masses are used.