The ability to accurately calculate the relative stabilities of numerous polymorphs of a given molecular crystal is crucial for the success of any molecular crystal structure prediction (CSP) approach. We have recently presented a hierarchical CSP procedure based on van-der-Waals-inclusive density functional theory [Hoja et al., 2018, arXiv:1803.07503], which yields excellent stability rankings for molecular crystals involving rigid molecules, salts, co-crystals, and highly polymorphic drug-like molecules. This approach includes many-body dispersion effects, exact exchange, as well as vibrational free energies. Here, we discuss in detail the impact of these effects on the obtained stability rankings. In addition, we assess the impact of the approximations used in our hierarchical procedure. We show that our procedure is generally robust to 1–2 kJ mol⁻¹ for the systems in the latest CSP blind test but vibrational free energies for crystals involving flexible molecules would benefit from directly including many-body dispersion interactions. In addition, we also discuss the effect of temperature on the structure of molecular crystals and a simple but effective method for estimating anharmonic effects.

中文翻译：

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用DFT + MBD方法对分子晶体多晶型物的第一性原理稳定性排名

准确计算给定分子晶体的多种多晶型物的相对稳定性的能力对于任何分子晶体结构预测（CSP）方法的成功至关重要。最近，我们提出了一种基于范德瓦尔斯式的密度泛函理论的分层CSP程序[Hoja et al。，2018，arXiv：1803.07503]，对于涉及刚性分子，盐，共晶体和高度多态性的类药物分子的分子晶体，其稳定性排名非常出色。这种方法包括多体分散效应，精确交换以及振动自由能。在这里，我们详细讨论这些影响对获得的稳定性排名的影响。此外，我们评估了分层过程中使用的近似值的影响。我们证明我们的程序通常对1-2 kJ mol ^-1是稳健的对于最新的CSP盲测试中的系统，但是包含柔性分子的晶体的振动自由能将直接受益于多体分散相互作用。此外，我们还讨论了温度对分子晶体结构的影响，以及一种简单而有效的估计非谐效应的方法。