forked from lijiext/lammps
75 lines
3.1 KiB
Plaintext
75 lines
3.1 KiB
Plaintext
"Higher level section"_Howto.html - "LAMMPS WWW Site"_lws - "LAMMPS
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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,Commands_all.html)
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:line
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Magnetic spins :h3
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The magnetic spin simulations are enabled by the SPIN package, whose
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implementation is detailed in "Tranchida"_#Tranchida.
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The model represents the simulation of atomic magnetic spins coupled
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to lattice vibrations. The dynamics of those magnetic spins can be used
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to simulate a broad range a phenomena related to magneto-elasticity, or
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or to study the influence of defects on the magnetic properties of
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materials.
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The magnetic spins are interacting with each others and with the
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lattice via pair interactions. Typically, the magnetic exchange
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interaction can be defined using the
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"pair/spin/exchange"_pair_spin_exchange.html command. This exchange
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applies a magnetic torque to a given spin, considering the orientation
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of its neighboring spins and their relative distances.
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It also applies a force on the atoms as a function of the spin
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orientations and their associated inter-atomic distances.
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The command "fix precession/spin"_fix_precession_spin.html allows to
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apply a constant magnetic torque on all the spins in the system. This
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torque can be an external magnetic field (Zeeman interaction), or an
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uniaxial magnetic anisotropy.
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A Langevin thermostat can be applied to those magnetic spins using
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"fix langevin/spin"_fix_langevin_spin.html. Typically, this thermostat
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can be coupled to another Langevin thermostat applied to the atoms
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using "fix langevin"_fix_langevin.html in order to simulate
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thermostatted spin-lattice systems.
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The magnetic Gilbert damping can also be applied using "fix
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langevin/spin"_fix_langevin_spin.html. It allows to either dissipate
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the thermal energy of the Langevin thermostat, or to perform a
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relaxation of the magnetic configuration toward an equilibrium state.
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The command "fix setforce/spin"_fix_setforce.html allows to set the
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components of the magnetic precession vectors (while erasing and
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replacing the previously computed magnetic precession vectors on
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the atom).
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This command can be used to freeze the magnetic moment of certain
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atoms in the simulation by zeroing their precession vector.
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The command "fix nve/spin"_fix_nve_spin.html can be used to
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perform a symplectic integration of the combined dynamics of spins
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and atomic motions.
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The minimization style "min/spin"_min_spin.html can be applied
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to the spins to perform a minimization of the spin configuration.
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All the computed magnetic properties can be output by two main
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commands. The first one is "compute spin"_compute_spin.html, that
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enables to evaluate magnetic averaged quantities, such as the total
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magnetization of the system along x, y, or z, the spin temperature, or
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the magnetic energy. The second command is "compute
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property/atom"_compute_property_atom.html. It enables to output all the
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per atom magnetic quantities. Typically, the orientation of a given
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magnetic spin, or the magnetic force acting on this spin.
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:line
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:link(Tranchida)
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[(Tranchida)] Tranchida, Plimpton, Thibaudeau and Thompson,
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Journal of Computational Physics, 372, 406-425, (2018).
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