The APIP package is based on the paper:

David Immel, Ralf Drautz, Godehard Sutmann; Adaptive-precision potentials for large-scale atomistic simulations. J. Chem. Phys. 14 March 2025; 162 (11): 114119. https://doi.org/10.1063/5.0245877

The pair_style pace/apip requires the installation of lib/pace of the ML-PACE package.
The installation of lib/pace is described in src/ML-PACE/README .

Examples of how to use an adaptive-precision potential are provided in examples/PACKAGES/apip .

in.vacancy contains a small example that can be used to visualize the transition region and get a visual impression of the selected parameters.
in.surface.balance in a more realistic example, in which a surface is simulated and the benefit of fix apip_atom_weight and fix balance for adaptive-precision interatomic potentials is demonstrated.

One can obtain a conservative adaptive-precision interatomic potential via local averaging of a differentiable descriptor as shown in

David Immel, Ralf Drautz, Godehard Sutmann; Conservative adaptive-precision interatomic potentials;  arXiv:2512.07693

and demonstrated with in.surface.la.cons , where the descriptor is calculated using the differentiable centro-symmetry parameter.
When the original CSP is used, the potential is not conservative any more when CSP-pairs change between timesteps as demonstrated with in.surface.la.nocons .
A load-balancing example for conservative adaptive-precision potentials is provided with in.surface.la.cons.balance .
Note that the switching parameter and the differentiation of the switching parameter are performed by a fix and, thus, cannot be included in the load balancing.
