Phase diagrams, thermodynamic properties and sound velocities derived from a multiple Einstein method using vibrational densities of states: an application to MgO–SiO₂

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• 作者：Michael H. G. Jacobs ; Rainer Schmid-Fetzer…
• 关键词：Equation of state ; Vibrational density of states ; Pressure scale ; Elasticity ; Anharmonicity
• 刊名：Physics and Chemistry of Minerals
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：44
• 期：1
• 页码：43-62
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Mineralogy; Crystallography and Scattering Methods; Geochemistry; Mineral Resources;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-2021
• 卷排序：44

文摘

In a previous paper, we showed a technique that simplifies Kieffer’s lattice vibrational method by representing the vibrational density of states with multiple Einstein frequencies. Here, we show that this technique can be applied to construct a thermodynamic database that accurately represents thermodynamic properties and phase diagrams for substances in the system MgO–SiO₂. We extended our technique to derive shear moduli of the relevant phases in this system in pressure–temperature space. For the construction of the database, we used recently measured calorimetric and volumetric data. We show that incorporating vibrational densities of states predicted from ab initio methods into our models enables discrimination between different experimental data sets for heat capacity. We show a general technique to optimize the number of Einstein frequencies in the VDoS, such that thermodynamic properties are affected insignificantly. This technique allows constructing clones of databases from which we demonstrate that the VDoS has a significant effect on heat capacity and entropy, and an insignificant effect on volume properties.