  We use the 1-bond -> 2-phonon percolation doublet of zincblende alloys as a
mesoscope for an unusual insight into their phonon behavior under pressure. We
focus on (Zn,Be)Se and show by Raman scattering that the original Be-Se doublet
at ambient pressure, of the stretching-bending type, turns into a pure-bending
singlet at the approach of the high-pressure ZnSe-like rocksalt phase, an
unnatural one for the Be-Se bonds. The freezing of the Be-Se stretching mode is
discussed within the scope of the percolation model (mesoscopic scale), with ab
initio calculations in support (microscopic scale).
