Substrate Al(111) | Medium 1 M HCl | DFT level B3LYP/6-311++G(d,p) (ddCOSMO:water) | Generated 2026-07-18 19:37
The molecules modelled here are screened in silico as representative candidates, not a verified analysis of any real sample. Confirm the actual composition experimentally (e.g. by LC-MS/GC-MS) before drawing firm conclusions.
1. Overview
corrosim pipeline
2. Summary & ranking
Of the 2 molecules screened, sulfamethoxazole ranks highest on the composite electronic score (+0.33), which averages three independent axes — a small HOMO–LUMO gap (4.02 eV), the Lukovits ΔN and the molecular dipole — the strongest all-round electron-donating profile of the set. It adsorbs flat on Al in the physisorption regime (E_ads ≈ -100 kJ/mol). The lead holds across all 2 descriptor bases evaluated (geometry and protonation). This is a computational screening prediction requiring electrochemical confirmation (see the Method section and caveats).
Sulfamethoxazole
Trimethoprim
Gap (eV)
4.02 ✓
4.154
ΔN
-0.07
-0.038
Dipole (D)
9.267
5.477
E_ads (kJ/mol)
-99.66
-130.18 ✓
Al–O (Å)
3.55
3.55
Score
0.333 ✓
-0.333
Ranking basis
Top candidate
force-field geometry, neutral
Sulfamethoxazole
force-field geometry, pH-weighted
Sulfamethoxazole
Lead robust: the same candidate tops all 2 descriptor bases (geometry and protonation).
Scored on three independent axes of the canonical basis (force-field geometry, pH-weighted; z-scored; higher = stronger): the HOMO–LUMO gap, the Lukovits ΔN (electron donation to the metal) and the dipole (a weak tie-breaker — its direction vs efficiency is disputed). The geometry / protonation panels below are a sensitivity check, not separate rankings. E_ads and the Al–O distance validate the lead, they do not enter the score. Full method: docs/pipeline.md.
3. DFT electronic descriptors
Modelled moleculesFrontier-orbital energies vs the metal work function
3.3 Species in the acidic medium (protonated cation)
Descriptor
Trimethoprim+H+
Sulfamethoxazole+H+
Formula
C14H19N4O3+
C10H12N3O3S+
HOMO (eV)
-6.494
-6.554
LUMO (eV)
-2.34
-2.534
Gap ΔE (eV)
4.154
4.02
η hardness (eV)
2.077
2.01
σ softness (1/eV)
0.482
0.498
χ electronegativity (eV)
4.417
4.544
ω electrophilicity (eV)
4.698
5.135
ΔN
-0.038
-0.071
E_back-donation (eV)
-0.519
-0.502
Dipole (D)
TNC
-5.686
-3.614
Protonated +1 cation descriptors in 1 M HCl; a component of the pH-weighted canonical basis (see the Summary), shown here on its own.
3.4 Speciation in 1 M HCl (pH ≈ -0.0)
0% neutral / 100% protonated at this pH — the protonated form dominates. Population-weighted descriptors (the speciation axis of the ranking ensemble; the headline ranks on the canonical basis):
Descriptor
Trimethoprim
Sulfamethoxazole
Formula
C14H18N4O3
C10H11N3O3S
HOMO (eV)
-6.494
-6.554
LUMO (eV)
-2.34
-2.534
Gap ΔE (eV)
4.154
4.02
η hardness (eV)
2.077
2.01
σ softness (1/eV)
0.482
0.498
χ electronegativity (eV)
4.417
4.544
ω electrophilicity (eV)
4.698
5.136
ΔN
-0.038
-0.07
E_back-donation (eV)
-0.519
-0.502
Dipole (D)
5.477
9.267
TNC
-5.686
-3.614
3.5 Local reactivity (Fukui)
Strongest electron-donating oxygens (highest f⁻) per molecule:
DFT level: B3LYP/6-311++G(d,p) (ddCOSMO:water). Global descriptors come from the frontier-orbital energies via Koopmans' theorem; ΔN uses the metal work function with η(metal) = 0. The Monte-Carlo and Brownian-MD stages use a classical van-der-Waals adsorption model — a physics-based screening surrogate, not a substitute for periodic DFT or for electrochemical validation. The composite ranking is a heuristic that orders candidates; it does not prove inhibition. Full methodology: docs/pipeline.md; validation record: docs/validation.md.
