Polyamorphism and Pressure-Induced Metallization at the Rigidity Percolation Threshold in Densified GeSe4 Glass

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• 作者：Bora Kalkan ; Ranga P. Dias ; Choong-Shik Yoo ; Simon M. Clark ; Sabyasachi Sen
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 13, 2014
• 年：2014
• 卷：118
• 期：10
• 页码：5110-5121
• 全文大小：839K
• 年卷期：v.118,no.10(March 13, 2014)
• ISSN：1932-7455

文摘

Chalcogenide glasses with tetrahedral networks can undergo significant densification under pressure owing to their open structures. The structural mechanisms of pressure-induced densification and the corresponding evolution of physical properties of glassy GeSe₄ alloy are studied over pressures ranging between ambient and 32.5 GPa, using X-ray scattering supplemented with 3D Monte Carlo structural modeling, Raman spectroscopy, electrical conductivity, and P鈥?i>V equation of state measurements. The results demonstrate a pressure-induced, hysteretically reversible transition between low-density semiconducting and high-density metallic amorphous phases of GeSe₄ near 10鈥?5 GPa. These two phases are characterized by their distinct P鈥?i>V equations of state and structural mechanisms of densification. Densification in the low-density phase is dominated by large inward shifting of the second neighbors with a small amount of conversion from edge-sharing to corner-sharing GeSe₄ tetrahedra. On the other hand, densification in the high-density phase involves a gradual increase in the nearest-neighbor coordination numbers of Ge and Se atoms and the formation of Ge鈥揋e bonds between adjacent polyhedral units. These structural transformations are accompanied by a pressure-induced metallization that is reversible.