Reversible and metastable changes in the raman spectrum of GeS₂ glass induced by compression

We report cryobaric Raman measurements for amorphous (a‐) GeS₂ at 13K to 56 kbar. Hydrostaticity in a diamond‐anvil cell is maintained by an argon pressure‐transmitting medium. Pressure‐induced peak shifts are fractionally small and reversible. However, peak broadenings are large (∼50–100%) and metastably retained, along with a newly emergent peak at 486cm⁻¹, after pressure release and dark‐annealing. We find evidence for pressure‐assisted quasicrystallization at P=56 kbar. These results support a molecular model in which pressure squeezes out free (intermolecular) volume. We estimate that internal stress‐fluctuations caused by random intercluster coupling do not exceed 2 kbar at P=0 (1 atm.). The metastable broadening is attributed to retained densification ∼20%. The 486cm⁻¹ peak, assigned to sulfur chain and/or ring modes, indicates S‐rich (presumably compensated by Ge‐rich) regions formed under pressure by fairly atomic rearrangements.