Sudden Reversal of the Defect-like Behavior of Small Rings in Vitreous Silica

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• 作者：S. Sen
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：August 16, 2007
• 年：2007
• 卷：111
• 期：32
• 页码：9431 - 9433
• 全文大小：54K
• 年卷期：v.111,no.32(August 16, 2007)
• ISSN：1520-5207

文摘

The structural response of vitreous silica to changes in temperature and pressure is of fundamental importancein earth and materials sciences and is largely controlled by the ring-size distribution that controls the topologyof the structure. The 3- and 4-membered rings constitute only a small fraction of the structure but are knownto be sensitive to and increase in concentration with increasing pressure and temperature. We present newexperimental results that show a sudden reversal in the temperature dependence of the concentrations ofthese rings near the recently discovered density minimum of vitreous silica. These results invalidate ourconventional wisdom regarding the entropically stabilized, defect-like behavior of the small rings and indicatethat these rings are possibly key players in controlling the density of silica.