# ACE1 and ACE1pack Documentation

ACE1.jl is a Julia package for parameterising interatomic potentials in terms of the atomic cluster expansion, i.e., body-ordered invariant polynomials. ACE1pack.jl provides a user-oriented and compatibility layer. These pages document ACE1pack and to some limited extent also the packages it depend on.

### Three Ways to Work with ACE1.jl

1. Fitting from the Command line.

ACE1pack provides scripts to fit potentials from the command line. Fitting is controlled by a dictionary of parameters in a .json file to specify the model and fitting options.

2. Using the ACE1pack wrapper functions in julia

ACE1pack also provides helper functions which wrap the functionality of ACE1.jl in julia.

3. Using ACE1.jl in julia directly.

Finally, it is possible to use the ACE1 julia code directly.

### References

• Drautz, R.: Atomic cluster expansion for accurate and transferable interatomic potentials. Phys. Rev. B Condens. Matter. 99, 014104 (2019). [DOI] [arxiv]

• G. Dusson, M. Bachmayr, G. Csanyi, S. Etter, C. van der Oord, and C. Ortner. Atomic cluster expansion: Completeness, efficiency and stability. J. Comp. Phys. 454, 110946, 2022. [DOI] [arxiv]