Relative Packing Efficiency in Hydrates

详细信息    查看全文

• 作者：H. Donald Brooke Jenkins ; Maja Ponikvar-Svet ; Joel F. Liebman
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2009
• 出版时间：September 10, 2009
• 年：2009
• 卷：54
• 期：9
• 页码：2722-2728
• 全文大小：189K
• 年卷期：v.54,no.9(September 10, 2009)
• ISSN：1520-5134

文摘

We define two parameters, Πb>iceb> and Πb>parentb>, estimated from hydrate and parent volumes, to be a measure of the efficiency of the packing of molecules in a hydrate compared on the one hand to that of idealized solid ice and on the other to the parent molecule from which the hydrate is derived. The packing efficiency ratio, Πb>iceb>[Mb>pb>·Xb>qb>·nHb>2b>O], is defined for a general hydrate Mb>pb>·Xb>qb>·nHb>2b>O containing p (complex) cations M^q+ and q (complex) anions X^p− by Πb>iceb>[hydrate] = [Vb>atb>(parent) − Vb>atb>(hydrate)]/[Vb>atb>(parent) − 0.0082] where Vb>atb>(parent) and Vb>atb>(hydrate) are the average volumes occupied per atom in the parent and hydrate structures, respectively, and 0.0082 corresponds to the average volume per atom in ice. All volumes are measured in units of nm³. Πb>parb>[hydrate] + Πb>iceb>[hydrate] = 1. Two simpler indices are studied, Π and Π*, and we explore the use of these as a means of categorizing hydrates and defining their domain of existence.