X-ray, Mössbauer spectroscopy, and extended x-ray absorption fine structure studies provide an atomic-scale description of the pressure-amorphized ${\mathrm{Ge}}_4$. At P>12 GPa a gradual onset of structural disorder accompanied by a molecular-association process is observed. An amorphized state concurring with the transformation of the molecular crystal into a metallic glass stabilizes at 25 GPa. It is accomplished by a gradual growth of a disordered (${\mathrm{GeI}}_4$${)}_{\mathit{n}}$ polymer, a phase characterized by enhanced Ge-I bond lengths and charge delocalization. Both phenomena are consistent with a ${\mathit{I}}_{5\mathit{p}}$→${\mathrm{Ge}}_{4\mathit{s}4\mathit{p}}$ charge-transfer band closure.

• Received 13 December 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.2733