RustBCA

RustBCA is a general-purpose, high-performance code for simulating ion-material interactions including sputtering, reflection, and implantation using the binary collision approximation (BCA), written in Rust! RustBCA includes a standalone version and libraries for including ion-material interactions in simulations written in C/C++, Python, and Fortran.

By discretizing the collision cascade into a sequence of binary collisions, BCA codes can accurately and efficiently model the prompt interaction between an energetic ion and a target material. This includes reflection, implantation, and transmission of the incident ion, as well as sputtering and displacement damage of the target. Generally, BCA codes can be valid for incident ion energies between several eV/nucleon to <1 GeV/nucleon. Improvements to RustBCA have expanded the regime of validity for some quantities, such as reflection coefficients, below 1 eV/nucleon for some ion/target pairs.

Check out the RustBCA Wiki for detailed information, installation instructions, use cases, examples, and more. See the RustBCA paper at the Journal of Open Source Software by clicking the badge below:

Selected citations of RustBCA as of 5/24/23: * Simulation of liquid lithium divertor geometry using SOLPS-ITER, JD Lore et al. (2022) * Characterizing W sources in the all-W wall, all-RF WEST tokamak environment, CC Klepper et al. (2022) * hPIC2: A hardware-accelerated, hybrid particle-in-cell code for dynamic plasma-material interactions, LT Meredith et al. (2023) * Global sensitivity analysis of a coupled multiphysics model to predict surface evolution in fusion plasma–surface interactions, P. Robbe et al. (2023) * Modeling the effect of nitrogen recycling on the erosion and leakage of tungsten impurities from the SAS-VW divertor in DIII-D during nitrogen gas injection, MS Parsons et al. (2023) * Enabling attractive-repulsive potentials in binary-collision-approximation monte-carlo codes for ion-surface interactions, J Drobny and D Curreli (2023) * Multi-physics modeling of tungsten collector probe samples during the WEST C4 He campaign, A. Lasa et al. (2024)

Getting started

The easiest way to get started is with the ergonomic Python functions. These functions use the default RustBCA options detailed on the Input Files page, which are not universally applicable. These examples use example material parameters located in scripts/materials.py that should be verified before use. Follow these steps to install, build, and run simple RustBCA simulations for sputtering yields and reflection coefficients: ``` git clone https://github.com/lcpp-org/rustbca cd rustbca python -m pip install . python Python 3.9.6 (tags/v3.9.6:db3ff76, Jun 28 2021, 15:26:21) [MSC v.1929 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information.

from libRustBCA import *; from scripts.materials import *; import numpy as np angle = 0.0 # deg energy = 1000.0 # eV numsamples = 10000 1 < sputteringyield(argon, tungsten, energy, angle, numsamples) < 1.1 # Y approx. 1.04 True RN, RE = reflectioncoefficient(argon, tungsten, energy, angle, numsamples) 0.3 < RN < 0.4 # RN approx. 0.35 True 0.0 < RE < 0.2 # R_E approx 0.1 True ```

For those eager to get started with the standalone code, try running one of the examples in the RustBCA/examples directory. Note that to automatically manipulate input files and reproduce the plots located on the Wiki, these may require some optional Python packages (matplotlib, numpy, scipy, shapely, and toml).

H trajectories and collision cascades in boron nitride

First, run the example using:

shell $ cargo run --release 0D examples/boron_nitride_0D.toml 2>/dev/null #suppress progress bar for automatic testing Processing 10 ions... Initializing with 4 threads... Finished!

Afterwords, fire up your favourite Python interpreter (e.g., IPython) and execute:

python from scripts.rustbca import * do_trajectory_plot("boron_nitride_")

He implantation into a layered TiO₂/Al/Si target

First, run the example using:

shell $ cargo run --release examples/layered_geometry.toml 2>/dev/null #suppress progress bar for automatic testing Processing 10000 ions... Initializing with 4 threads... Finished!

Afterwords, fire up your favourite Python interpreter (e.g., IPython) and execute:

```python import numpy as np import matplotlib.pyplot as plt

depositedions = np.genfromtxt( "2000.0eV0.0001degHeTiO2AlSideposited.output", delimiter=",", names=["M", "Z", "x", "y", "z", "collisions"], )

plt.hist(deposited_ions["x"], bins=100)

plt.show() ```

Features

The following features are implemented in RustBCA:

• Ion-material interactions for all combinations of incident ion and target species.
• Infinite, homogeneous targets (Mesh0D), Layered, finite-depth inhomogeneous targets (Mesh1D), arbitrary 2D composition through a triangular mesh (Mesh2D), fast homogeneous 2D geometry (Homogeneous2D), homogeneous spherical geometry (Sphere), and homogeneous 3D triangular mesh geometry (TriMesh).
• Amorphous Solid/Liquid targets, Gaseous targets, and targets with both solid/liquid and gaseous elements
• Low energy (< 25 keV/nucleon) electronic stopping modes including:
  • local (Oen-Robinson),
  • nonlocal (Lindhard-Scharff),
  • and equipartition
• Biersack-Varelas interpolation is also included for electronic stopping up to ~1 GeV/nucleon. Note that high energy physics beyond electronic stopping are not included, and that Biersack-Varelas may not be as accurate as other methods.
• Biersack-Haggmark treatment of high-energy free-flight paths between collisions can be included to greatly speed up high-energy simulations (i.e., by neglecting very small angle scattering).
• A wide range of interaction potentials are provided, including:
  • the Kr-C, ZBL, Lenz-Jensen, and Moliere universal, screened-Coulomb potentials.
  • the Lennard-Jones 12-6 and Morse attractive-repulsive potentials.
• Solving the distance-of-closest-approach problem is achieved using:
  • the Newton-Raphson method for purely repulsive potentials,
  • or, for attractive-repulsive potentials, an Adaptive Chebyshev Proxy Rootfinder with Automatic Subdivision algorithm and a polynomial root-finding algorithm are provided through rcpr.
• Multiple interaction potentials can be used in a single simulation for any number of potentials/species.
  • For example, the He-W interaction can be specified using a Lennard-Jones 12-6 potential, while the W-W interaction can be defined using a Kr-C potential.
• The scattering integral can be calculated using:
  • Gauss-Mehler quadrature,
  • Gauss-Legendre quadrature,
  • Mendenall-Weller quadrature,
  • or the MAGIC algorithm (for certain screened Coulomb potentials only).
• Input files use the TOML format, making them both human-readable and easily parsable.
• RustBCA generates user-friendly, context-providing error messages, which help pinpoint the cause of errors and provide suggested fixes to the user.
• The simulation results are comma-delimited (csv format) and include:
  • the energies and directions of emitted particles (reflected ions and sputtered atoms),
  • the final positions of implanted ions,
  • displacements,
  • full trajectory tracking for both the incident ions and target atoms,
  • and many other parameters such as position of origin of sputtered particles and energy loss along trajectories.
• Optionally, the code can produce energy-angle and implantation distributions when built with the --features distributions flag and disable space-intensive particle list output with --features no_list_output.
• Library functions for modeling ion reflection, implantation, and sputtering in C++/C, Python, and Fortran codes.

Installation

Without optional features, RustBCA should compile with cargo alone on Windows, MacOS, and Linux systems:

cargo build --release

will add an executable at target/release/.

HDF5 for particle list input has been tested on Windows, but version 1.10.6 must be used.

Manual Dependences

• rustup, the Rust toolchain (includes cargo, the Rust package manager, rustc, the Rust compiler, and more).

Automatic Dependencies

• see Cargo.toml for a complete list of required and optional dependencies managed by cargo.

Optional Dependencies

• HDF5 libraries
• For manipulating input files and running associated scripts, the following are suggested:
  • Python 3.6+
  • Python libraries: numpy, matplotlib, toml, shapely, and scipy.

Detailed instructions for Ubuntu 18.04 LTS

1. (Optional) Install Python 3.6+ (this comes natively in Ubuntu 18.04)
2. Install curl: bash sudo apt-get install curl
3. Install rustup, the Rust toolchain (includes rustc, the compiler, and cargo, the package manager) from https://rustup.rs/ by running the following command and following on-screen instructions: bash curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
4. (Optional) Install pip for Python: bash sudo apt-get install python3-pip
5. (Optional) Install Python libraries for making input files: bash python3 -m pip install numpy matplotlib shapely scipy toml
6. (Optional - should come with rustup) Install cargo: bash sudo apt-get install cargo
7. Build RustBCA: bash git clone https://github.com/lcpp-org/RustBCA cd RustBCA cargo build --release
8. (Optional) Build RustBCA with optional dependencies, hdf5 and/or rcpr: bash cargo build --release --features cpr_rootfinder,hdf5
9. input.toml is the input file - see the Input File page for more information
10. Run the required tests using: bash cargo test
11. (Optional) Run the tests for the advanced rootfinder: bash cargo test --features cpr_rootfinder

Detailed instructions for Fedora 33

Most of the ingredients for building RustBCA and running the Python helper scripts are available natively in the Fedora software repository, so the setup is relatively painless.

The Rust toolchain can be aquired using:

bash sudo dnf install rust rust-src rust-std-static rust-analysis rust-gdb rust-lldb rustfmt

The (optional) Python packages can be obtained using:

bash sudo dnf install python3-numpy python3-scipy python3-matplotlib python3-toml python3-shapely

or, alternatively, using pip3.

Building RustBCA is straightforward, and can be done using:

bash git clone https://github.com/lcpp-org/rustBCA cd RustBCA cargo build --release

with all of the explicit dependencies listed in Cargo.toml handled automatically during the build.

Usage

To use RustBCA, modify an input.toml file, which is used to configure each simulation. To run a simulation, execute:

bash ./RustBCA

with input.toml in the same directory as RustBCA.

Alternatively, RustBCA accepts the name of a.toml input file as a single command line argument.

bash ./RustBCA /path/to/input.toml

Additionally, RustBCA accepts an input file type (one of: 0D, 1D, 2D, TRIMESH, SPHERE - see the wiki for more details): bash ./RustBCA 0D /path/to/input.toml Warning: RustBCA defaults to the 2D triangular mesh input mode. For more details, see Input Files. Also have a look at the examples on the Wiki to see some examples of RustBCA input files.