Selvauma/hc-na-interface-deepmd

Hard-Carbon | NaPF₆ EC:DEC Interface — Bare vs. MgO-Coated (DeepMD)

What this is

Two DeepMD-kit potentials for a sodiated hard-carbon (HC) anode in contact with a NaPF₆ EC:DEC liquid electrolyte — a Na-ion battery SEI-formation / Na-plating study, comparing a bare electrode against an MgO-coated one.

	bare	MgO-coated
Composition	C₁₃₄F₁₂H₅₀Na₂O₂₄P₂	C₁₃₄F₁₂H₅₀Mg₂₀Na₂O₄₄P₂
Cell size	224 atoms	264 atoms
Coating	—	amorphous MgO (Mg–O ≈ 1.93 Å, Mg–Mg ≈ 2.74 Å)
Sodiation x (Na/C)	0.0149	0.0149 (matched)
Capacity	33.1 mAh/g	33.1 mAh/g

Both cells are fully periodic (no vacuum) electrode|electrolyte interfaces, electrolyte = NaPF₆ salt in EC:DEC solvent, PF₆⁻ confirmed intact by geometry in both. The MgO coating sits directly between the HC surface and the electrolyte, letting the two potentials isolate the coating's effect on SEI formation and Na-plating behavior under otherwise-identical conditions.

Files & Validation

File	RMSE energy (eV/atom)	RMSE force (eV/Å)	Training steps	Size
model/HC_MgO_interface.pb	0.00131	0.202	500,000	362.7 MB
model/HC_bare_interface.pb	0.00292	0.269	500,000	247.4 MB

RMSE values are validation-set (held-out) energy/force error, read directly from each run's DeepMD-kit lcurve.out at its final training step — not re-derived or estimated.

Training pipeline

Interface DFT relaxation → AIMD (VASP, PBE) → DeepMD-kit train/freeze/ compress → classical-tier electrolyte-only reference (19,888-atom OPLS-AA box) for cross-checking bulk electrolyte behavior. Produced by HPCA (github.com/selvachandrasekaranselvaraj/hpca). MACE fine-tunes for both systems are still training (not yet included — see the MLIP inventory notes).

Citation

Selva Chandrasekaran Selvaraj, University of Illinois Chicago. Manuscript in preparation: "HC-Na | NaPF₆ EC:DEC Interface: SEI Formation and Na Plating" (bare and MgO-coated variants).