"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Commands_all.html)

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pair_style spin/dmi command :h3

[Syntax:]

pair_style spin/dmi cutoff :pre

cutoff = global cutoff pair (distance in metal units) :ulb,l

:ule

[Examples:]

pair_style spin/dmi 4.0
pair_coeff * * dmi 2.6 0.001 1.0 0.0 0.0
pair_coeff 1 2 dmi 4.0 0.00109 0.0 0.0 1.0 :pre

[Description:]

Style {spin/dmi} computes the Dzyaloshinskii-Moriya (DM) interaction
between pairs of magnetic spins.
According to the expression reported in "(Rohart)"_#Rohart, one has
the following DM energy:

:c,image(Eqs/pair_spin_dmi_interaction.jpg)

where si and sj are two neighboring magnetic spins of two particles,
eij = (ri - rj)/|ri-rj| is the unit vector between sites i and j,
and D is the DM vector defining the intensity (in eV) and the direction
of the interaction.

In "(Rohart)"_#Rohart, D is defined as the direction normal to the film oriented
from the high spin-orbit layer to the magnetic ultra-thin film.

The application of a spin-lattice Poisson bracket to this energy (as described
in "(Tranchida)"_#Tranchida5) allows to derive a magnetic torque omega, and a
mechanical force F (for spin-lattice calculations only) for each magnetic
particle i:

:c,image(Eqs/pair_spin_dmi_forces.jpg)

More details about the derivation of these torques/forces are reported in
"(Tranchida)"_#Tranchida5.

For the {spin/dmi} pair style, the following coefficients must be defined for
each pair of atoms types via the "pair_coeff"_pair_coeff.html command as in
the examples above, or in the data file or restart files read by the
"read_data"_read_data.html or "read_restart"_read_restart.html commands, and
set in the following order:

rc (distance units)
|D| (energy units)
Dx, Dy, Dz  (direction of D) :ul

Note that rc is the radius cutoff of the considered DM interaction, |D| is
the norm of the DM vector (in eV), and Dx, Dy and Dz define its direction.

None of those coefficients is optional.  If not specified, the {spin/dmi}
pair style cannot be used.

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[Restrictions:]

All the {pair/spin} styles are part of the SPIN package.  These styles
are only enabled if LAMMPS was built with this package, and if the
atom_style "spin" was declared.  See the "Build
package"_Build_package.html doc page for more info.

[Related commands:]

"atom_style spin"_atom_style.html, "pair_coeff"_pair_coeff.html,
"pair_eam"_pair_eam.html,

[Default:] none

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:link(Rohart)
[(Rohart)] Rohart and Thiaville,
Physical Review B, 88(18), 184422. (2013).
:link(Tranchida5)
[(Tranchida)] Tranchida, Plimpton, Thibaudeau and Thompson,
Journal of Computational Physics, 372, 406-425, (2018).
