"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/neel command :h3

[Syntax:]

pair_style spin/neel cutoff :pre

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

:ule

[Examples:]

pair_style spin/neel 4.0
pair_coeff * * neel 4.0 0.0048 0.234 1.168 2.6905 0.705 0.652
pair_coeff 1 2 neel 4.0 0.0048 0.234 1.168 0.0 0.0 1.0 :pre

[Description:]

Style {spin/neel} computes the Neel pair anisotropy model
between pairs of magnetic spins:

:c,image(Eqs/pair_spin_neel_interaction.jpg)

where si and sj are two neighboring magnetic spins of two particles,
rij = ri - rj is the inter-atomic distance between the two particles,
eij = (ri - rj)/|ri-rj| is their normalized separation vector and g1,
q1 and q2 are three functions defining the intensity of the dipolar
and quadrupolar contributions, with:

:c,image(Eqs/pair_spin_neel_functions.jpg)

With the functions g(rij) and q(rij) defined and fitted according to
the same Bethe-Slater function used to fit the exchange interaction:

:c,image(Eqs/pair_spin_exchange_function.jpg)

where a, b and d are the three constant coefficients defined in the
associated "pair_coeff" command.

The coefficients a, b, and d need to be fitted so that the function
above matches with the values of the magneto-elastic constant of the
materials at stake.

Examples and more explanations about this function and its
parameterization are reported in "(Tranchida)"_#Tranchida6. More
examples of parameterization will be provided in future work.

From this DM interaction, each spin i will be submitted to a magnetic
torque omega and its associated atom to a force F (for spin-lattice
calculations only).

More details about the derivation of these torques/forces are reported
in "(Tranchida)"_#Tranchida6.

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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(Tranchida6)
[(Tranchida)] Tranchida, Plimpton, Thibaudeau and Thompson,
Journal of Computational Physics, 372, 406-425, (2018).
