This package contains a fix rigid/nvt/mspin command that updates nanoparticle dynamics subjected to external magnetic field and mangetic dipolar interactions.

It also contains commands to compute the externel field interaction energy, dipolar interaction energy, and interparticle distance during simulation.

See the doc page for the fix rigid/nvt/mspin or the compute mspin/energy or compute mspin/distance commands for detailed usage instructions.

Use of this package requires LAMMPS to be built with the RIGID package.

There are example scripts for using commands in this package in the examples/mspin directory.

The authors of the package is Akhlak U. Mahmood (amahmoo3 at ncsu dot edu) and Yaroslava G. Yingling (yara_yingling at ncsu dot edu) at North Carolina State University, USA. Contact the authors directly if you have questions.

Developed for simulation method described in:

A.U. Mahmood and Y.G. Yingling. All-Atom Simulation Method for Zeeman Alignment and Dipolar Assembly of Magnetic Nanoparticles. Journal of Chemical Theory and Computation (2022) doi:10.1021/acs.jctc.1c01253.

git clone https://github.com/yingling-group/lammps-mspin.git
cd lammps-mspin
mkdir build
cd build
cmake -C ../cmake/presets/mspin.cmake ../cmake
make -j4

Please update the cmake/presets/mspin.cmake preset file according to your machine's configuration before building.

This package adds one fix and two computes. Please see the following doc files for usage details.

• doc/src/fix_rigid_mspin.rst
• doc/src/compute_mspin_distance.rst
• doc/src/compute_mspin_energy.rst

List of all modifications:

$ git diff lammps/stable --name-only

cmake/CMakeLists.txt
cmake/presets/mspin.cmake
doc/src/compute_mspin_distance.rst
doc/src/compute_mspin_energy.rst
doc/src/fix_rigid_mspin.rst
examples/mspin/README.md
examples/mspin/data.mspin
examples/mspin/in.mspin
examples/mspin/log.3Aug2022.g++.1
examples/mspin/log.3Aug2022.g++.4
src/MSPIN/README.md
src/MSPIN/compute_mspin.cpp
src/MSPIN/compute_mspin.h
src/MSPIN/compute_mspin_distance.cpp
src/MSPIN/compute_mspin_distance.h
src/MSPIN/fix_mspin_nh.cpp
src/MSPIN/fix_mspin_nh.h
src/MSPIN/fix_mspin_nvt.cpp
src/MSPIN/fix_mspin_nvt.h
src/Makefile
src/RIGID/fix_rigid.cpp

Other than adding the package specific files in the src/MSPIN, doc/src and examples/mspin directories, the following changes are made to the official LAMMPS files.

• src/RIGID/fix_rigid.cpp updated to allow additional arguments.
• src/Makefile updated to add the name of the package to the make PACKAGE list.
• cmake/CMakeList.txt updated to add the name of the pacakge to the cmake STANDARD_PACKAGES list.
• .github directory removed.

Jan 20, 2023

• Updated to the latest LAMMPS stable branch. 88c8b6ec6feac6740d140393a0d409437f637f8b
• Modified the source code to add and use a custom atom property for the qm magnetic charge values.