Pressure‐Dependent Cr 3+ Luminescence Elucidated by Spectroscopic Analysis and Ab Initio Calculations

Luminescent manometry enables noncontact pressure sensing at small scales and under extreme conditions, yet its development remains constrained by the limited sensitivity and single‐mode response of commercial materials, as well as the absence of a comprehensive theoretical framework for pressure induced spectral evolution. To address these challenges, we selectively chose the Sr 3 Al 2 Ge 4 O 14 host where the cation disorder stabilizes multiple nonequivalent Cr 3+ centers, producing coexisting narrow‐line and broadband emissions across 0–10.06 GPa. This coexistence of narrow‐line and broadband emissions provides multiple complementary readout channels based on spectral shifts and luminescence intensity ratios, indicating the potential of this phosphor for multimodal pressure readout under compression. Ab initio calculations of pressure dependent excited states produce configurational coordinate diagrams that clearly reveal how compression perturbs excited state energies and alters equilibrium Cr─O bond lengths. These insights rationalize the opposite pressure shifts of narrow line and broadband emissions and their intensity variations. Crucially, a correlation between excitation‐induced bond length changes and pressure dependent spectral shifts was identified, showing that direction and magnitude of structural response upon excitation govern high pressure luminescence. This combined experimental‐theoretical study provides mechanistic insight into pressure‑dependent Cr 3+ luminescence and a framework that may guide the development of improved optical pressure probes.