分子晶体相的多极小特性对自由能的影响
Implications of the multi-minima character of molecular crystal phases onto the free energy
AI总结：
本研究以N-(4-Methylbenzylidene)-4-methylalanine分子晶体为例，探讨分子晶体相的多极小特性对自由能的影响，提出包含构型熵和振动熵的量子叠加框架，证明忽略多极小特性会导致约200 K的转变温度误差，强调考虑构型熵对获得可靠自由能排序的必要性。
摘要：
近年来，计算方法的显著进步极大地提高了确定分子晶体不同相能量排序的精度。这些进展主要集中在提供精确的色散校正交换相关泛函，以及在有限温度下描述振动熵对自由能贡献的方法。最近发现，几种分子晶体相具有多极小特性。在我们的研究中，我们以由N-(4-Methylbenzylidene)-4-methylalanine组成的分子晶体为例，重点探讨其多极小特性。我们在完整的DFT水平上或使用拟合到DFT数据的机器学习势来探索其势能景观。我们不仅计算了许多局部极小值，还计算了沿转化路径的精确能垒，以证明我们系统的多极小特性。此外，我们提出了一个基于量子叠加方法的框架，该框架同时包含构型熵和振动熵。作为示例，我们展示了对于我们的系统，如果不考虑多极小特性，其两个相之间的转变温度会产生约200 K的误差。这表明，为了获得复杂分子晶体可靠的有限温度自由能排序，考虑构型熵是绝对必要的。
英文摘要：
In recent years, significant advancements in computational methods have dramatically enhanced the precision in determining the energetic ranking of different phases of molecular crystals. The developments mainly focused on providing accurate dispersion corrected exchange correlation functionals and methods for describing the vibrational entropy contributions to the free energy at finite temperatures. Several molecular crystals phases were recently found to have of multi-minima character. For our investigations we highlight the multi-minima character in the example of the molecular crystal consisting of N-(4-Methylbenzylidene)-4-methylalanine. We explore its potential energy landscape on the full DFT level or with a machine learned potential that was fitted to DFT data. We calculate not only many local minima but also exact barriers along transformation pathways to demonstrate the multi-minima character of our system. Furthermore, we present a framework, based on the quantum superposition method, that includes both configurational and vibrational entropy. As an example, we show for our system that the transition temperature between two of its phases is afflicted by an error of about 200 K if the multi-minima character is not taken into account. This indicates that it is absolutely essential to consider configurational entropy to obtain reliable finite temperature free energy rankings for complex molecular crystals.
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