Molecular Implementation of the Machine-Learned Skala Exchange-Correlation Functional in CP2K through GauXC
Abstract
Machine-learned exchange--correlation (XC) functionals offer a route to improve Kohn--Sham density-functional theory without incurring the cost of explicitly correlated electronic-structure methods. Their use in production simulation codes, however, requires a well-defined mapping between the learned model and the host-code density representation. We formulate and implement a Skala-1.1 interface in CP2K through the external GauXC library. CP2K supplies the geometry, Gaussian basis, spin-resolved atomic-orbital density matrix, and communicator, while GauXC evaluates the XC energy, atomic-orbital potential matrix, and available nuclear derivatives. The interface accepts both all-electron and valence-only density matrices. The latter may arise from separable dual-space pseudopotentials or molecular effective-core potentials. Implementation errors are isolated from functional differences by comparing the Perdew--Burke--Ernzerhof (PBE) functional evaluated through GauXC with native CP2K PBE. The resulting interface gives consistent energies, forces validated against finite-difference total-energy checks, and force-based molecular-virial diagnostics for representative molecular cases. The dietGMTKN55 benchmark suite is evaluated with an all-electron Gaussian augmented plane-wave treatment for elements up to bromine and def2 effective-core potentials for the heavier elements. The resulting aggregate mean absolute deviation of 1.255 kcal/mol is within 0.012 kcal/mol of the corresponding Skala reference value of 1.243 kcal/mol. This work establishes a validated molecular implementation of Skala in CP2K through GauXC.
Related
- Native implementation of the machine-learned Skala exchange-correlation functional in CP2K: Unified one-centre reconstruction for molecular and condensed-phase calculations
- Machine-learned Laplacian-level density functional from exact exchange-correlation potentials and energies
- Influence of exchange–correlation functional on machine-learnt interatomic potentials accuracy: a systematic study in borosilicate glasses
- Influence of Exchange–Correlation Functional on Machine-Learned Interatomic Potentials’ Accuracy: A Systematic Study of Borosilicate Glasses
- Stationarity Constraints Improve Both Energies and Densities of Machine-Learned Exchange-Correlation Functionals
BibTeX
@misc{poschel2026molecular,
title = {{Molecular Implementation of the Machine-Learned Skala Exchange-Correlation Functional in CP2K through GauXC}},
author = {Franz Pöschel and Johann Pototschnig and Frederick Stein and Andreas Knüpfer and Thijs Vogels and Stefano Battaglia and Sebastian Ehlert and Jürg Hutter and Thomas D. Kühne},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.19033},
eprint = {2608.19033},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.19033},
}
RIS
TY - UNPB
TI - Molecular Implementation of the Machine-Learned Skala Exchange-Correlation Functional in CP2K through GauXC
AU - Franz Pöschel
AU - Johann Pototschnig
AU - Frederick Stein
AU - Andreas Knüpfer
AU - Thijs Vogels
AU - Stefano Battaglia
AU - Sebastian Ehlert
AU - Jürg Hutter
AU - Thomas D. Kühne
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2608.19033
UR - https://arxiv.org/abs/2608.19033
AB - Machine-learned exchange--correlation (XC) functionals offer a route to improve Kohn--Sham density-functional theory without incurring the cost of explicitly correlated electronic-structure methods. Their use in production simulation codes, however, requires a well-defined mapping between the learned model and the host-code density representation. We formulate and implement a Skala-1.1 interface in CP2K through the external GauXC library. CP2K supplies the geometry, Gaussian basis, spin-resolved atomic-orbital density matrix, and communicator, while GauXC evaluates the XC energy, atomic-orbital potential matrix, and available nuclear derivatives. The interface accepts both all-electron and valence-only density matrices. The latter may arise from separable dual-space pseudopotentials or molecular effective-core potentials. Implementation errors are isolated from functional differences by comparing the Perdew--Burke--Ernzerhof (PBE) functional evaluated through GauXC with native CP2K PBE. The resulting interface gives consistent energies, forces validated against finite-difference total-energy checks, and force-based molecular-virial diagnostics for representative molecular cases. The dietGMTKN55 benchmark suite is evaluated with an all-electron Gaussian augmented plane-wave treatment for elements up to bromine and def2 effective-core potentials for the heavier elements. The resulting aggregate mean absolute deviation of 1.255 kcal/mol is within 0.012 kcal/mol of the corresponding Skala reference value of 1.243 kcal/mol. This work establishes a validated molecular implementation of Skala in CP2K through GauXC.
ER -