corrosim — multiscale corrosion-inhibitor report

Substrate Fe(110)  |  Medium 1 M HCl  |  DFT level B3LYP/6-311++G(d,p) (ddCOSMO:water)  |  Generated 2026-07-18 18:23

1. Overview

2. Summary & ranking

Of the 3 molecules screened, quercetin ranks highest on the composite electronic score (+0.70), which averages three independent axes — a small HOMO–LUMO gap (3.59 eV), the Lukovits ΔN and the molecular dipole — the strongest all-round electron-donating profile of the set. It adsorbs flat on Fe in the physisorption regime (E_ads ≈ -16 kJ/mol). The lead holds across all 4 descriptor bases evaluated (geometry and protonation). This is a computational screening prediction requiring electrochemical confirmation (see the Method section and caveats).

Lead robust: the same candidate tops all 4 descriptor bases (geometry and protonation).

Scored on three independent axes of the canonical basis (DFT-relaxed 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 Fe–O distance validate the lead, they do not enter the score. Full method: docs/pipeline.md.

3. DFT electronic descriptors

3.1 Frontier-orbital isosurfaces (HOMO / LUMO)

3.2 Full descriptor table (neutral, aqueous)

3.3 Geometry refinement (FF vs DFT-optimised)

3.4 Optimised-geometry descriptors (DFT-relaxed)

Sensitivity: descriptors on the DFT-relaxed geometry (the geometry axis of the ranking ensemble). The headline ranks on the canonical basis; see the Summary.

Optimised protonated cations (in-acid)

3.5 Species in the acidic medium (protonated cation)

Protonated +1 cation descriptors in 1 M HCl; a component of the pH-weighted canonical basis (see the Summary), shown here on its own.

3.6 Speciation in 1 M HCl (pH ≈ -0.0)

97% neutral / 3% protonated at this pH — the neutral form dominates. Population-weighted descriptors (the speciation axis of the ranking ensemble; the headline ranks on the canonical basis):

Computed pKaH (DFT deprotonation cycle)

B3LYP/6-311++G(d,p) + ddCOSMO deprotonation cycle (frequency-corrected).

3.7 Local reactivity (Fukui)

Strongest electron-donating oxygens (highest f⁻) per molecule:

• Kaempferol: O3 (f⁻=0.116), O12 (f⁻=0.055), O19 (f⁻=0.053)
• Quercetin: O3 (f⁻=0.090), O9 (f⁻=0.088), O11 (f⁻=0.040)
• Isorhamnetin: O9 (f⁻=0.094), O3 (f⁻=0.093), O11 (f⁻=0.043)

3.8 Electrostatic-potential (ESP) map

4. Monte Carlo adsorption

5. Brownian MD — Fe–donor RDF

6. Method & caveats

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.