有限温度第一原理热力学：关于处理有序相和无序相的观点-中国材料进展

文章信息/Info

Title:: First-principles thermodynamics at finite temperatures: Perspective on ordered and disordered phases

Author(s):: ShunLi Shang; Yi Wang; and Zi-Kui Liu; Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

摘要:: 第一原理计算一个悬而未决的难题是预测无序相在有限温度下的热力学性能。我们指出该难题的最新解决思路是采用可以处理微观组态的配分函数方法，该方法已成为处理只有一种微观组态构成的有序相以及有多种微观组态构成的无序相的关键。结合第一原理声子计算和准简谐近似可以有效地预测任意一个给定微观组态的热力学性质。本文总结了我们在第一原理热力学方面的最新研究进展并具体给出了有序相方面的例子：Li2S, hcp Mg和fcc Ni、以及无序相方面的例子：Cu2ZnSnS4 (CZTS) 和fcc Ce。本文同时指出：（i）从常用的“相”扩展到“微观组态”开辟了一条定量研究材料相变、热膨胀等异常性能的新途径，而这些异常性能的起源可以追溯到“微观组态构型熵”；并且（ii）这些微观组态也可以认为是材料基因组的基本组成模块。

Abstract:: A longstanding issue of first-principles calculations is to predict thermodynamic properties for a disordered phase at finite temperatures. Here, we shows that a recent advance for this issue is the partition function approach in terms of microstates, which is the key for both ordered phase with one primary microstate and disordered phase consisting of two and more noticeable microstates. For a given microstate, first-principles phonon calculations in terms of the quasiharmonic approach provide a practical pathway to predict its thermodynamic properties. In the present paper, a summary of properties predicted at finite temperatures is presented, and examples are given for ordered phases of anti-fluorite Li2S, hcp Mg, and fcc Ni as well as disordered phases of Cu2ZnSnS4 (CZTS) and fcc Ce. It is shown that (i) the extension from “phase” to “microstate” opens an avenue to quantitatively tailor anomalous properties such as phase transition and thermal expansion anomaly, and these anomalies are traceable from the microstate configurational entropy, and (ii) these microstates can be considered as the building blocks, i.e., the genome, of materials.