Nanochemistry Research Institute, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
Inorg Chem. 2013 Jan 18;52(2):992-8. doi: 10.1021/ic3022479. Epub 2013 Jan 4.
Formation enthalpies, Δ(f)H(298), are essential thermodynamic descriptors of the stability of materials, with many available from the numerous thermodynamic databases. However, there is a need for predictive methods to supplement these databases with missing values for known and even hypothetical materials, and also as an independent check on the not-always reliable published values. In this paper, we present 34 additive single-ion values, Δ(f)H(298)(ion), from the formation enthalpies of 124 ionic solids, including an extensive group of silicates. In addition, we have also developed an additive set of 29 single-ion formation Gibbs energies, Δ(f)G(298)(ion), for a smaller group of 42 materials from within the full set, constrained by the limited availability of the corresponding experimental data. Such single-ion values may be extended among related materials using simple differences from known thermodynamic values, but always with critical consideration of the results. Using the excellent available data for silicates, we propose that the solid-state silicate ion formation enthalpies can be estimated as -Δ(f)H(298)(silicate)/kJ mol(-1)= -252[n(Si) + n(O)] - 27, where n(X) represents the number of species X in the silicate. More speculatively, we estimate the contribution per silicon and oxygen species as -490 and -184 kJ mol(-1), respectively. Similarly, -Δ(f)G(298)(silicate)/kJ mol(-1)= -266[n(Si) + n(O)] - 7, with the contribution per silicon and oxygen species being -140 and -300 kJ mol(-1), respectively. We compare and contrast these results with the extensive collection of "modified lattice energy" (MLE) ion parameters from the M.S. thesis of C. D. Ratkey. Our single-ion formation enthalpies and the MLE parameters may be used in complementary predictions. While lattice energies, U(POT), entropies, S(o)(298), and heat capacities, C(p,298), of ionic solids are reliably estimated as proportional to their formula volumes (using our Volume-Based Thermodynamic, VBT, procedures), this is not the case in general for thermodynamic formation properties, other than within select groups of related materials.
形成焓（Δ(f)H(298)）是材料稳定性的重要热力学描述符，许多热力学数据库中都有可用的数据。然而，需要有预测方法来补充这些数据库中已知甚至假设材料的缺失值，并且作为对并不总是可靠的已发表值的独立检查。在本文中，我们提出了 34 个来自 124 种离子固体形成焓的加和单离子值（Δ(f)H(298)(ion)），包括广泛的硅酸盐组。此外，我们还为完整组中的 42 种材料开发了一套加和的 29 个单离子形成吉布斯能（Δ(f)G(298)(ion)），这是一组较小的材料，受相应实验数据有限可用性的限制。可以使用来自已知热力学值的简单差异在相关材料之间扩展此类单离子值，但始终要批判性地考虑结果。使用硅酸盐的优秀可用数据，我们提出可以将固态硅酸盐离子形成焓估计为-Δ(f)H(298)(silicate)/kJ mol(-1)=-252[n(Si)+n(O)]-27，其中 n(X) 表示硅酸盐中 X 物种的数量。更推测性地，我们估计每个硅和氧物种的贡献分别为-490 和-184 kJ mol(-1)。类似地，-Δ(f)G(298)(silicate)/kJ mol(-1)=-266[n(Si)+n(O)]-7，其中硅和氧物种的贡献分别为-140 和-300 kJ mol(-1)。我们将这些结果与 C. D. Ratkey 的 M.S. 论文中广泛收集的“改良晶格能”（MLE）离子参数进行了比较和对比。我们的单离子形成焓和 MLE 参数可用于互补预测。虽然离子固体的晶格能（U(POT)）、熵（S(o)(298)）和热容（C(p,298)）可以可靠地估计为与其分子式体积成正比（使用我们的基于体积的热力学（VBT）程序），但在一般情况下，除了在特定的相关材料组内，热力学形成性质并非如此。
