pyridine C5H5N

A_6e858b26e5 · SMILES c1ccncc1 · InChIKey JUJWROOIHBZHMG-UHFFFAOYSA-N

Anchored

finite-difference Hessian noisy

finite-difference Hessian noisy (analytic check differs > 15 cm⁻¹). The finite-difference Hessian and the analytic Hessian of the same geometry differ by more than 15 cm⁻¹ on at least one frequency; the numerical route is the noisy one.

Infrared spectrum at the anchor level (CCSD(T)/cc-pVDZ + [MP2/cc-pVTZ − MP2/cc-pVDZ]; rung 4, anchored)

Band heights: not computed for this molecule yet (no dipole derivatives); positions only. Compared with the cheap Hessian (B3LYP, analytic): frequency rms 19.1 cm⁻¹.

Structure

2D depiction from the SMILES.

Status ladder

Listed
Cheap level done
Correction predicted — not yet: the learned layer is training
Spectrum predicted — not yet: the learned layer is training
Anchored — evidence
Validated

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Harmonic frequencies at the cheap level (deck v1: B3LYP and ωB97X, 6-31G*, at the B3LYP geometry)

27 vibrational modes; imaginary modes negative. Shift = ωB97X − B3LYP.

Both functionals are drawn in the anchor chart above; the table lists the values of the corpus.

#	B3LYP (cm⁻¹)	ωB97X (cm⁻¹)	shift
1	386.6	404.6	+18.1
2	421.8	432.9	+11.1
3	613.5	618.2	+4.7
4	658.8	657.5	-1.2
5	718.8	730.8	+12.0
6	763.2	774.8	+11.5
7	898.1	912.4	+14.3
8	956.3	983.9	+27.6
9	993.3	1023.2	+30.0
10	1009.7	1028.3	+18.6
11	1012.0	1033.8	+21.7
12	1051.1	1060.8	+9.7
13	1086.6	1089.5	+2.9
14	1101.0	1107.0	+6.0
15	1178.7	1189.5	+10.8
16	1253.3	1260.5	+7.1
17	1307.6	1272.7	-35.0
18	1397.8	1398.6	+0.8
19	1486.5	1492.4	+5.9
20	1531.2	1543.4	+12.1
21	1637.8	1673.7	+36.0
22	1644.0	1680.4	+36.3
23	3169.3	3208.0	+38.7
24	3171.2	3214.5	+43.3
25	3191.2	3234.0	+42.8
26	3206.6	3249.3	+42.8
27	3214.8	3257.5	+42.7

Second route

Analytic Hessian (pyscf, grid 99/590) against the corpus finite differences: b3lyp max |Δω| 12 cm⁻¹; wb97x max |Δω| 17 cm⁻¹.

Provenance

Releases: none yet
Entered the corpus as: parent molecules chosen by hand (benzene, naphthalene, the PAH cores and their relatives) (layer A)
Coupled-cluster anchor: CCSD(T)/cc-pVDZ + [MP2/cc-pVTZ − MP2/cc-pVDZ]
Anchor spectrum: Hessian composite_full_pyridine_2026-10-07.npz
Imaginary modes: B3LYP 0, ωB97X 0
Source files: corpus factory · manifest