It is found that samples of crystalline germanium brought rapidly (<1 s) to ambient pressure from 14 GPa transform to the so-called BC8 structure rather than to the ST12 structure that is found on slower pressure decrease. The BC8 phase is unstable at atmospheric pressure, but we have been able to record angle-dispersive powder patterns within less than 30 minutes of pressure release using an image-plate detector on a synchrotron source. The refined crystal structure of BC8-Ge is very similar to that found previously for BC8-Si.

• Received 20 April 1993

DOI:https://doi.org/10.1103/PhysRevB.48.9883