Basis sets
SIESTA uses a numerical atomic orbital (NAO) basis set. The Basis Set panel in the studio lets you choose the size and shape of the basis for each species.
Basis size
The most common choices are:
- SZ (single-zeta) — minimal basis, fast but less accurate.
- DZ (double-zeta) — two radial functions per orbital, better convergence.
- DZP (double-zeta polarized) — adds polarization orbitals; the recommended default for most calculations.
- TZP / TZDP — triple-zeta variants for high-accuracy work.
Per-species customization
In the basis panel you can override the basis size or energy shift per species.
Advanced users can edit the %block PAO.BasisSizes block directly in the FDF
preview.