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Manuscript Title: SPILADY: A Parallel CPU and GPU Code for Spin-Lattice Magnetic Molecular Dynamics Simulations
Authors: Pui-Wai Ma, S. L. Dudarev, C. H. Woo
Program title: SPILADY, version 1.0
Catalogue identifier: AFAN_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 207(2016)350
Programming language: OpenMP C/C++, CUDA C/C++.
Computer: Any computer with an OpenMP capable C/C++ compiler or computer with CUDA capable GPU card and an nvcc compiler.
Operating system: Linux, Unix, Windows.
RAM: At least 500MB, depending on the number of atoms or atomic spins, and on the simulation type.
Keywords: Spin-lattice dynamics, molecular dynamics, spin dynamics.
PACS: 05.10.-a, 02.60.Cb, 95.75.Pq, 75.10.-b.
Classification: 7.7.

Nature of problem:
Excitation of magnetic degrees of freedom affects a broad range of properties of magnetic materials, including their equilibrium crystal structure and response to mechanical deformation. Existing atomistic simulation methods, for example molecular dynamics, do not treat magnetic degrees of freedom and do not describe the effect of magnetism on interatomic forces. This is addressed by the spin-lattice dynamics approach. The integration algorithm satisfies the requirement of phase volume conservation in the multi-dimensional space of atomic coordinates, velocities, and atomic spins, which is achieved through the application of the symplectic Suzuki-Trotter decomposition. Numerical solutions of spin-lattice dynamics equations retain high accuracy over extended intervals of time.

Solution method:
An atomic scale simulation technique for modelling the coupled dynamics of atomic coordinates and spins. The method generalizes molecular dynamics to the case of magnetic materials, and uses a parallel Suzuki-Trotter decomposition-based time integration algorithm.

The current version assumes a single chemical element material com- position. The spin Hamiltonian and equations of motion assume isotropic magnetic interactions. Evolution equations assume the validity of localized magnetic moment approximation.

Unusual features:
An open source spin-lattice dynamics code. The time integration algorithm uses the Suzuki-Trotter decomposition, which is a symplectic integration method retaining high accuracy over extended intervals of time. The code can be executed in parallel on multiple CPUs using OpenMP directives, or on an Nvidia GPU card.

Additional comments:
Further information available on website: http://spilady.ccfe.ac.uk

Running time:
Similar to molecular dynamics, from several minutes to several weeks or months, depending on the number of atoms or spins involved in a simulation, and on the type of the simulation.