Commit modifs before release 2 (04/02/18)

6.24 "Setting parameters for the kspace_style pppm/disp command"_#howto_24

6.25 "Polarizable models"_#howto_25

6.26 "Adiabatic core/shell model"_#howto_26

6.27 "Drude induced dipoles"_#howto_27 :all(b)

6.27 "Drude induced dipoles"_#howto_27

6.28 "Magnetic spins"_#howto_28 :all(b)

The example input scripts included in the LAMMPS distribution and

highlighted in "Section 7"_Section_example.html also show how to

4   2

5   3

6   3

The interactions between the 

7   4

8   4

(...) :pre

similar from the CORESHELL package if the core and Drude particle come

too close, which can cause numerical issues.

:line

6.28 Magnetic spins :link(howto_28),h4

The magnetic spin simualtions are enabled by the SPIN package, whose

implementation is detailed in "Tranchida"_#Tranchida7.

The model representents the simulation of atomic magnetic spins coupled 

to lattice vibrations. The dynamics of those magnetic spins can be used 

to simulate a broad range a phenomena related to magneto-elasticity, or 

or to study the influence of defects on the magnetic properties of 

materials. 

The magnetic spins are interacting with each others and with the 

lattice via pair interactions. Typically, the magnetic exchange 

interaction can be defined using the 

"pair/spin/exchange"_pair_spin_exchange.html command. This exchange

applies a magnetic torque to a given spin, considering the orientation

of its neighboring spins and their relative distances. 

It also applies a force on the atoms as a function of the spin 

orientations and their associated inter-atomic distances. 

The command "fix precession/spin"_fix_precession_spin.html allows to

apply a constant magnetic torque on all the spins in the system. This

torque can be an external magnetic field (Zeeman interaction), or an

uniaxial magnetic anisotropy. 

A Langevin thermostat can be applied to those magnetic spins using 

"fix langevin/spin"_fix_langevin_spin.html. Typically, this thermostat 

can be coupled to another Langevin thermostat applied to the atoms 

using "fix langevin"_fix_langevin.html in order to simulate 

thermostated spin-lattice system. 

The magnetic Gilbert damping can also be applied using "fix 

langevin/spin"_fix_langevin_spin.html. It allows to either dissipate 

the thermal energy of the Langevin thermostat, or to perform a 

relaxation of the magnetic configuration toward an equilibrium state.

All the computed magnetic properties can be outputed by two main 

commands. The first one is "compute spin"_compute_spin.html, that 

enables to evaluate magnetic averaged quantities, such as the total 

magnetization of the system along x, y, or z, the spin temperature, or

the magnetic energy. The second command is "compute 

property/atom"_compute_property_atom.html. It enables to output all the

per atom magnetic quantities. Typically, the orientation of a given 

magnetic spin, or the magnetic force acting on this spin.

:line

:line

:link(howto-Lamoureux)

[(Lamoureux and Roux)] G. Lamoureux, B. Roux, J. Chem. Phys 119, 3025 (2003)

:link(Tranchida7)

[(Tranchida)] Tranchida, Plimpton, Thibaudeau and Thompson, 

arXiv preprint arXiv:1801.10233, (2018).

                        x, y, z, xs, ys, zs, xu, yu, zu, ix, iy, iz,

                        vx, vy, vz, fx, fy, fz,

                        q, mux, muy, muz, mu,

			sp, spx, spy, spz, fmx, fmy, fmz,

                        radius, diameter, omegax, omegay, omegaz,

                        angmomx, angmomy, angmomz,

                        shapex,shapey, shapez,

      q = atom charge

      mux,muy,muz = orientation of dipole moment of atom

      mu = magnitude of dipole moment of atom

      sp = atomic magnetic spin moment

      spx, spy, spz = direction of the atomic magnetic spin

      fmx, fmy, fmz = magnetic force

      radius,diameter = radius,diameter of spherical particle

      omegax,omegay,omegaz = angular velocity of spherical particle

      angmomx,angmomy,angmomz = angular momentum of aspherical particle

compute 1 all property/atom xs vx fx mux

compute 2 all property/atom type

compute 1 all property/atom ix iy iz :pre

compute 1 all property/atom ix iy iz 

compute 3 all property/atom sp spx spy spz :pre

[Description:]

corresponding attribute is in, e.g. velocity units for vx, charge

units for q, etc.

For the spin quantities, sp is in the units of the Bohr magneton, spx,

spy, and spz are adimentional quantities, and fmx, fmy and fmz are 

given in rad.THz. 

[Restrictions:] none

[Related commands:]

:line

fix integration/spin command :h3

fix nve/spin command :h3

[Syntax:]

fix ID group-ID integration/spin keyword values :pre

fix ID group-ID nve/spin keyword values :pre

ID, group-ID are documented in "fix"_fix.html command :ulb,l

integration/spin = style name of this fix command :l

nve/spin = style name of this fix command :l

keyword = {lattice} :l

  {lattice} value = {no} or {yes} :pre

:ule

[Examples:]

fix 3 all integration/spin lattice yes

fix 1 all integration/spin lattice no :pre

fix 3 all nve/spin lattice yes

fix 1 all nve/spin lattice no :pre

[Description:]

By default (lattice = yes), a spin-lattice integration is performed.

The {integration/spin} fix applies a Suzuki-Trotter decomposition to 

The {nve/spin} fix applies a Suzuki-Trotter decomposition to 

the equations of motion of the spin lattice system, following the scheme:

:c,image(Eqs/fix_integration_spin_stdecomposition.jpg)

SPIN package. See the "Making LAMMPS"_Section_start.html#start_3

section for more info on packages.

When the spin algorithm is used for serial calculations, it is 

necessary to define a map via the atom_modify command. 

Typically, by adding the command:

To use the spin algorithm, it is necessary to define a map with 

the atom_modify command. Typically, by adding the command:

atom_modify map array :pre

:line

fix force/spin command :h3

fix precession/spin command :h3

[Syntax:]

fix ID group force/spin style args :pre

fix ID group precession/spin style args :pre

ID, group are documented in "fix"_fix.html command :ulb,l

force/spin = style name of this fix command :l

precession/spin = style name of this fix command :l

style = {zeeman} or {aniso} :l

  {zeeman} args = H x y z 

    H = intensity of the magnetic field (in Tesla)

[Examples:]

fix 1 all force/spin zeeman 0.1 0.0 0.0 1.0

fix 1 all force/spin aniso 0.001 0.0 0.0 1.0 :pre

fix 1 all precession/spin zeeman 0.1 0.0 0.0 1.0

fix 1 all precession/spin aniso 0.001 0.0 0.0 1.0 :pre

[Description:]

[Restrictions:]

The {force/spin} style is part of the SPIN package. 

The {precession/spin} style is part of the SPIN package. 

This style is only enabled if LAMMPS was built with this package, and

if the atom_style "spin" was declared. 

See the "Making LAMMPS"_Section_start.html#start_3 section for more info.

compute 	outsp all property/atom spx spy spz sp fmx fmy fmz

dump 		100 all custom 1 dump_cobalt_hcp.lammpstrj type x y z c_outsp[1] c_outsp[2] c_outsp[3]

run 		20000

run 		2000