Luminescence Spectra Simulation of Ce ³⁺ ‐Activated Phosphors by Accumulating Emission Lines Along First‐Principles Molecular Dynamics Trajectories

ABSTRACT To simulate the luminescence emission spectra of Ce 3+ ‐activated phosphors, we propose a method based on scalar‐relativistic density functional theory with corrections for on‐site Coulomb interactions, and first‐principles molecular dynamics (FPMD) calculations, accounting for atomic thermal motion beyond harmonic oscillations. The FPMD calculations at finite temperature were performed with the excited‐state (ES) electron configuration corresponding to the Ce 4f 0 5d 1 state. Subsequently, the transition energies and probabilities of 4f 0 5d 1 →4f 1 5d 0 transitions in each FPMD snapshot were calculated using the N −1 electron configuration in which the highest occupied level in the ground‐state (GS) configuration is vacated. This is justified because applying Janak's theorem to a flat‐band system allows each Kohn‐Sham orbital's energy to be regarded as the total energy of an ES generated by an excitation from the highest level. The time‐averaged spectrum was calculated by accumulating emission lines at the transition energies with amplitudes proportional to the probabilities. The spectra calculated for Ce 3+ ‐activated yttrium aluminum garnet exhibit shapes and positions that resemble those measured at temperatures above 300 K. The peak energies and full widths at half maximum at 300 K for the series of Ce 3+ ‐activated phosphors correlate with the experimental values, demonstrating the potential for predicting emission spectra of novel phosphors.