# Fast calculation of structural parameters and autocorrelation functions
`fastatomstruct` is a Python package (mostly written in Rust) that includes functions to calculate atomic structural quantities.
If possible, thread-based parallelization (using [`rayon`](https://crates.io/crates/rayon)) is employed to speed up calculations and take advantage of multicore processors.
## Documentation
[The documentation can be found here.](https://ag-salinga.zivgitlabpages.uni-muenster.de/fastatomstruct)
## What can this package do?
The package can currently calculate the following quantities:
- Structural
- Atomic distances
- Coordination numbers
- Nearest neighbours
- Radial distribution function
- Static structure factor
- Bond orientational parameter (Steinhardt et al.) and Bond Order Correlation parameter
- Tetrahedral order parameter
- Angular-limited three-body correlation (ALTBC)
- Bond length ratio (BLR)
- Dynamical
- Mean squared displacement
- Non-gaussian parameter
- Four-point correlation functions
- Autocorrelation (with and without interpolation)
## Example usage
This example uses the [Atomistic Simulation Environment](https://wiki.fysik.dtu.dk/ase/), which can also be installed using pip (`pip install ase`) and is now a dependency of `fastatomstruct`.
```python
from ase.build import bulk
from fastatomstruct import all_distances, coordination_numbers
# Lithium in the BCC phase with the unit cell repeated
# 10x10x10 times
atoms = bulk("Li", "bcc", 3.45).repeat((10, 10, 10))
# Atomic distances
dists = all_distances(atoms)
# Coordination numbers with a cutoff of 3 A
coordination = coordination_numbers(atoms, 3)
```
## Installation
### From PyPI
`fastatomstruct` can be installed from the [Python Package Index](https://pypi.org/project/fastatomstruct/). **Currently, only Linux with a Python version >= 3.7 is supported. In addition, your processor has to be x86-64 with AVX2 support.** Most processors since 2015 should meet those criteria. If your system doesn't, you can still install `fastatomstruct` from source (see next subsection).
To run the installation, use
```
pip install fastatomstruct
```
### From source
Installing `fastatomstruct` from source requires
- Python >= 3.7
- pip
- a working Rust installation (1.56 and newer), including cargo
- `maturin`, a Python package that can e.g. be installed using `pip3 install --upgrade maturin`
To build the Python wheel, run
```
maturin build --release
```
The resulting wheel will be located in `target/wheels/`. You can install it using
```
python3 -m pip install target/wheels/fastatomstruct-version.whl
```
Replace "version" with your actual Python version.
The package can then be used in Python using e.g. `from fastatomstruct import coordination_numbers`.
