PRESSURE-INDUCED AMORPHIZATION OF GEI4 MOLECULAR-CRYSTALS

X-ray, Mossbauer spectroscopy, and extended x-ray absorption fine stru cture studies provide an atomic-scale description of the pressure-amor phized GeI4. At P > 12 GPa a gradual onset of structural disorder acco mpanied 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 gradua l growth of a disordered (GeI4)n polymer, a phase characterized by enh anced Ge-I bond lengths and charge delocalization. Both phenomena are consistent with a I5p --> Ge4s4p charge-transfer band closure.