Hard Sphere Monte Carlo Simulation

This is my personal project to study Monte-Carlo simulations of monodispersed hard spheres in 3D.

It is not very fast. If you need large scale simulation, maybe you want to use hoomd-blue.

Install

You need to have Eigen and pybind11 to build the code. The project can be built with CMake, normally you will do,

mkdir build
cd build
cmake ..
make
make install

As a result, the python module (with name chard_sphere.cpython-xx-xxx.so) will be created in folder lib, as well as the static C++ library (libhard_sphere.a).

Python Frontend

The user is expceted to interact with the library via the Python interface. Typically, one shuold

1. copy the file chard_sphere.cpython-xx-xxx.so to the working directory; or
2. add the folder lib to $PYTHONPATH.

After that, you should be able to execute the command from hsmc import chard_sphere in Python.

Use the Code in Python

The following snippest present the way to start a simulation

from hsmc import chard_sphere
from hsmc.analysis import dump_xyz, TCCOTF
import numpy as np


n_particle = 1000
box = [30, 50, 60]  # box size in X, Y, and Z
is_pbc = [True, True, False]  # no PBC in the z-direction
is_hard = [False, False, True]  # hard walls along z-direction
r_skin = 5.0

# create the system
system = chard_sphere.HSMC(
    n=n_particle, box=box,
    is_pbc=is_pbc, is_hard=is_hard, r_skin=r_skin
)

# randomly fill non-overlapping hard spheres
system.fill_hs()

# reduce the box size slowly to reach desired volume fraction
system.crush(0.50, 0.02)

# print the overview of the system
print(system)


# perform 1000 Monte-Carlo sweeps, collect the configuration every 100 frames

configurations = np.empty((10, n_particle, 3))
for i in range(10):
    for _ in range(100):
        system.sweep()

    # retrieve the positions of the particles
    positions = system.get_positions()
    configurations[i] = positions.T

    # save the positions into an xyz file
    dump_xyz(
        'hard_sphere.xyz', positions.T,
        comment="box:[" + ",".join([  # write box as the comment
            f"{L:.8f} (PBC? {p}; Hard? {h})"
            for L, p, h in zip(system.get_box(), is_pbc, is_hard)
        ]) + "]"
    )