18. Zero-Phonon Line Calculations

The zero-phonon line (ZPL) is the optical transition energy between the relaxed ground and excited electronic states, excluding phonon sideband contributions. The same configuration-coordinate workflow can be applied to different defects, molecules, and materials by computing the relevant ground-state and excited-state total energies.

This section introduces the RESCU workflow for ZPL calculations through a worked example for the negatively charged nitrogen-vacancy center in diamond.

• 18.1. Zero-phonon line of the NV^- center in diamond