Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University, Perth 6845, Western Australia, Australia.
Inorg Chem. 2011 Sep 5;50(17):8565-9. doi: 10.1021/ic201093p. Epub 2011 Aug 3.
Thermodynamic properties, such as standard entropy, among others, have been shown to correlate well with formula volume, V(m), thus permitting prediction of these properties on the basis of chemical formula and density alone, with no structural detail required. We have termed these procedures "volume-based thermodynamics" (VBT). We here extend these studies to ambient isobaric heat capacities, C(p,m), of a wide range of materials. We show that heat capacity is strongly linearly correlated with formula volume for large sets of minerals, for ionic solids in general, and for ionic liquids and that the results demonstrate that the Neumann-Kopp rule (additivity of heat capacity contributions per atom) is widely valid for ionic materials, but the smaller heat capacity contribution per unit volume for ionic liquids is noted and discussed. Using these correlations, it is possible to predict values of ambient (298 K) heat capacities quite simply. We also show that the heat capacity contribution of water molecules of crystallization is remarkably constant, at 41.3 ± 4.7 J K(-1) (mol of water)(-1), so that the heat capacities of various hydrates may be reliably estimated from the values of their chemical formula neighbors. This result complements similar observations that we have reported for other thermodynamic differences of hydrates.
热力学性质，如标准熵等，已经被证明与公式体积 V(m) 有很好的相关性，因此可以仅根据化学式和密度来预测这些性质，而无需任何结构细节。我们将这些程序称为“基于体积的热力学”（VBT）。在这里，我们将这些研究扩展到了广泛的材料的环境等压热容 C(p,m)。我们表明，热容对于大量的矿物质、一般的离子固体以及离子液体来说，与公式体积有很强的线性相关性，结果表明，Neumann-Kopp 规则（每个原子的热容贡献的可加性）对于离子材料是广泛有效的，但注意到并讨论了离子液体的单位体积热容贡献较小的问题。使用这些相关性，可以非常简单地预测环境（298 K）热容的值。我们还表明，结晶水分子的热容贡献非常恒定，为 41.3 ± 4.7 J K(-1) (mol of water)(-1)，因此可以从其化学公式相邻物的值可靠地估计各种水合物的热容。这一结果补充了我们对水合物其他热力学差异的类似观察。
