# Quantum Module Guide

The Quantum module covers ground-state DFT, multi-electron atoms, and molecular benchmarks.

## Tabs

- **Atomic** — Kolos-Wolniewicz H₂ ground state, hydrogenic spectra.
- **DFT** — Clementi-Roetti atomic ground states.
- **Molecular** — bond energies, vibrational modes.

## Canonical benchmark

H₂ ground state recovered to chemical accuracy (1 mEh) against the Kolos-Wolniewicz reference.

## Why eV-scale zone tessellation

The Quantum module configures GeoNum zones tightly around atomic energy levels (1 eV to 100 eV). Without this, multi-electron correlations accumulate IEEE 754 error faster than the physics drift.

## References

- Kolos & Wolniewicz 1968, J. Chem. Phys. 49, 404 (H₂)
- Clementi & Roetti 1974, At. Data Nucl. Data Tables 14 (atomic ground states)
- Parr & Yang 1989, "Density-Functional Theory of Atoms and Molecules"