LAMMPS-Python script to use the molten spheres algorithm to perform athermal irradiation.
The algorithm is described at: https://doi.org/10.1016/j.actamat.2025.120814
Reali, L., Boleininger, M., Mason, D. R., & Dudarev, S. L. (2025). Atomistic simulations of athermal irradiation creep and swelling of copper and tungsten at high dose. Acta Materialia.

Please cite this paper if you make use of this script.


LAMMPS must be compiled as a shared library linked to Python 3+ with the numpy, scipy, and mpi4py packages.
The script is distributed on an "AS IS" basis without warranties or conditions of any kind, either express or implied.

The main programme is in moltenspheres.py. Simulation parameters are in a .json file in json folder.

Tested with LAMMPS version 29 Aug 2024.

Run with e.g.
>> mpirun -np 8 python3 moltenspheres.py json/Cu.json 


The script can be adapted to create an arcdpa-like plot with number of defects for a given molten sphere radius. Instead of overlapping events N times, one can use LAMMPS's clear command and have N independent runs with a single insertion (need to redefine several things inside the insertion loop if this is the case). 
The script can also be adapted to work with a distribution of sphere radii to mimic the effect of a spectrum of recoils. One can take a recoil spectrum and convert it to a frequency distribution for R, and then e.g. use numpy.random.choice() using the distribution of the radii to weigh the random number generation.