First principles calculations on the effect of pressure on SiHb>4b>(Hb>2b>)b>2b>

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• 作者：K.V. Shanavas ; ¹ ; ^{shanavas@barc.gov.in} ; H.K. Poswal ; Surinder M. Sharma
• 关键词：A. Molecular solid ; D. Phase transitions ; E. First principles ; E. High pressure
• 刊名：Solid State Communications
• 出版年：2012
• 期刊代码：101_00381098
• 类别：ms
• 出版时间：May, 2012
• 卷：152
• 期：10
• 页码：873-877
• 文件大小：655 K

摘要

The effect of pressure on the strength of Hb>2b> covalent bond in the molecular solid SiHb>4b>(Hb>2b>)b>2b> has been investigated using quantum molecular dynamics simulations and charge density analysis. Our calculations show, in agreement with the implications of the experimental results, that substantial elongation of Hb>2b> bond can be achieved at low pressures, with the onset of rapid changes close to 40聽GPa. Model calculations show redistribution of charge from bonding to antibonding states to be responsible for the behavior. Our computed Raman spectra confirm the dynamic exchange of hydrogen atoms speculated to be operative in SiHb>4b>-Db>2b> mixture by experiments. This exchange is shown to be a three step process driven by thermal fluctuations.