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首页> 外文期刊>Contributions to Mineralogy and Petrology >The accuracy of standard enthalpies and entropies for phases of petrological interest derived from density-functional calculations
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The accuracy of standard enthalpies and entropies for phases of petrological interest derived from density-functional calculations

机译：标准焓和培养物阶段阶段的精度源自密度函数计算

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The internal energies and entropies of 21 well-known minerals were calculated using the density functional theory (DFT), viz. kyanite, sillimanite, andalusite, albite, microcline, forsterite, fayalite, diopside, jadeite, hedenbergite, pyrope, grossular, talc, pyrophyllite, phlogopite, annite, muscovite, brucite, portlandite, tremolite, and CaTiO3-perovskite. These thermodynamic quantities were then transformed into standard enthalpies of formation from the elements and standard entropies enabling a direct comparison with tabulated values. The deviations from reference enthalpy and entropy values are in the order of several kJ/mol and several J/mol/K, respectively, from which the former is more relevant. In the case of phase transitions, the DFT-computed thermodynamic data of involved phases turned out to be accurate and using them in phase diagram calculations yields reasonable results. This is shown for the Al2SiO5 polymorphs. The DFT-based phase boundaries are comparable to those derived from internally consistent thermodynamic data sets. They even suggest an improvement, because they agree with petrological observations concerning the coexistence of kyanite+quartz+corundum in high-grade metamorphic rocks, which are not reproduced correctly using internally consistent data sets. The DFT-derived thermodynamic data are also accurate enough for computing the P-T positions of reactions that are characterized by relatively large reaction enthalpies (100kJ/mol), i.e., dehydration reactions. For reactions with small reaction enthalpies (a few kJ/mol), the DFT errors are too large. They, however, are still far better than enthalpy and entropy values obtained from estimation methods.
机译：使用密度泛函理论（DFT），VIZ计算21种众所周知的矿物质的内部能量和熵。 Kyanite，Sillimanite，Andalusite，Albite，微管，Forsterite，Fayalite，Diopside，翡翠，海燕胶质，Pyrope，Grossular，Talc，Percophyllite，Phlogopite，Annite，Muscovite，Brucite，Portlandite，Tremolite和Catio3-Perovskite。然后将这些热力学量转化为从元件和标准熵的形成标准焓，使得与表格值直接比较。与参考焓和熵值的偏差分别为几kJ / mol和几个j / mol / k的顺序，前者更相关。在相变的情况下，涉及阶段的DFT计算的热力学数据旨在准确，并在相图中使用它们，从而产生合理的结果。这显示为Al2SiO5多晶型物。基于DFT的相边界与来自内部一致热力学数据集的那些相当。他们甚至建议改进，因为他们同意岩浆物理观察，该观察在高档变质岩石中的kyanite +石英+刚玉的共存，这不会使用内部一致的数据集正确再现。 DFT衍生的热力学数据也足够精确，以计算特征在于相对大的反应焓（＆ 100kJ / mol），即脱水反应的对反应的P-T位置。对于小反应焓（几kJ / mol）的反应，DFT误差太大了。然而，它们仍然比从估计方法获得的焓和熵值更好。

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