the FCC lattice and its properties entirely on its own.

![Transformational energy barriers. We compare ANI-Al and various classical potentials to reference DFT data. (a) Volume-conserving Bain path energies. (b) Generalized Stacking Fault Energy (GSFE) slip path. (c) GSFE twinning path.[]{data-label="fig:bain_sf"}](images/Bain-SF_paper.pdf){width="1.0\columnwidth"}

Predicting energy barriers in crystal
-------------------------------------

The Bain path represents a volume-preserving homogeneous deformation that transforms between FCC and BCC crystals. Starting from the initial FCC cell ($c/a$= 1), we compress along one of the $\langle 100 \rangle$ directions (length $c$) while expanding equally in the two orthogonal directions (lengths $a=b$). The special value of $c/a=$ 1/$\sqrt{2} \approx 0.71$ would correspond to BCC symmetry. Figure \[fig:bain\_sf\]a shows energies along this Bain path, in which $c/a$ varies continuously while conserving volume, $a^2 c$. We compare ANI-Al to DFT reference calculations, as well as seven EAM-based potentials [@Mendelev2008AnalysisCu; @Sjostrom2016MultiphaseTheory; @Liu2004AluminiumEnergy; @Mishin1999InteratomicCalculations; @Zope2003InteratomicSystem; @Winey2009AAluminum; @Pascuet2015AtomicAlloy; @Sheng2011HighlyMetals]. Figure S3 of the SI provides the errors for each method along these paths. The observed maximum at $c/a=$ 1/$\sqrt{2}$ indicates that the BCC structure is unstable to tetragonal deformation.

A stacking fault in FCC represents a planar defect in which the crystal locally is in HCP configuration within the nearest neighbor shell (note that FCC 