THE COMPUTATIONAL INVESTIGATION OF THE PHASE-TRANSITION FROM THE GEO2ALPHA-QUARTZ STRUCTURE TO THE RUTILE STRUCTURE

We report a detailed computational investigation using several techniq ues relating to the phase transition from the alpha-quartz to the ruti le structure for GeO2 and GeO2/SiO2 solid solutions. We calculate an a ctivation barrier of approximately 47 kJ mol(-1) for the phase transit ion, which is in good agreement with the most recently reported experi mental value. We also identify a number of interesting intermediate st ructures, in which Ge is present in two coordination environments (fou rfold and sixfold). These complex intermediates have characteristics a kin to the experimentally observed amorphous systems. (C) 1996 Academi c Press.