The Dopant Cage Sets the Phonon Count of Lanthanide Emitters

Abstract

Multiphonon relaxation decides whether a lanthanide ion emits light or heats its host. Since 1968 it has been predicted from the host’s maximum phonon energy, although the excitation resides on a single ion. First-principles force constants and five decades of relaxation measurements show that the accepting vibration is the stretch of the dopant’s coordination cage, a site property set by local chemistry. Aliovalent substitution stiffens the cage by up to 27%, and across seven halide hosts the cage frequency departs from the host frequency by −21% to +19%. It predicts measured effective phonon frequencies three times more accurately than the host frequency, and in its quanta the seven energy-gap laws share one room-temperature slope. The site-resolved laws map the lattice limits of optical refrigeration from 2 to 6 µm. The phonon count of a lanthanide emitter becomes a site property that chemistry can tune and theory can compute before synthesis.

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BibTeX RIS

BibTeX

@misc{bian2026dopant,
  title = {{The Dopant Cage Sets the Phonon Count of Lanthanide Emitters}},
  author = {Daqian Bian},
  howpublished = {ChemRxiv},
  year = {2026},
  month = oct,
  doi = {10.26434/chemrxiv.15010222/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010222/v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - The Dopant Cage Sets the Phonon Count of Lanthanide Emitters
AU  - Daqian Bian
PY  - 2026
DA  - 2026/10/11
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15010222/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010222/v1
AB  - Multiphonon relaxation decides whether a lanthanide ion emits light or heats its host. Since 1968 it has been predicted from the host’s maximum phonon energy, although the excitation resides on a single ion. First-principles force constants and five decades of relaxation measurements show that the accepting vibration is the stretch of the dopant’s coordination cage, a site property set by local chemistry. Aliovalent substitution stiffens the cage by up to 27%, and across seven halide hosts the cage frequency departs from the host frequency by −21% to +19%. It predicts measured effective phonon frequencies three times more accurately than the host frequency, and in its quanta the seven energy-gap laws share one room-temperature slope. The site-resolved laws map the lattice limits of optical refrigeration from 2 to 6 µm. The phonon count of a lanthanide emitter becomes a site property that chemistry can tune and theory can compute before synthesis.
ER  -

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