A unified approach for calculating free energies of liquid and defective crystals based on thermodynamic integration
A unified approach for calculating free energies of liquid and defective crystals based on thermodynamic integration
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基于热力学积分计算液体和缺陷晶体自由能的统一方法
DOI：
10.1063/5.0095638
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发表时间：
2022
影响因子：
4.4
通讯作者：
Lijun Liu
中科院分区：
文献类型：
--
作者：
Jinping Luo;Chenyang Zhou;Qihang Li;Lijun Liu
自由能计算在物理、化学和材料研究中具有重要意义。热力学积分是估算自由能的最常用方法。在研究中，我们提出了一个统一的方法，使用原子模拟来计算液体和缺陷晶体的自由能。新的方法是基于热力学集成使用两个炼金术途径。软核势是为三体原子间相互作用势而开发的，以实现炼金术的途径。采用新的方法，可以计算液体的自由能，而不需要另一个参考系统。缺陷晶体的自由能可以在高温下直接计算。该方法避免了目前广泛应用的爱因斯坦晶体法中因缺陷扩散而导致的积分端点奇异性问题。此外，新的方法可以捕获整个自由能的缺陷晶体，包括非谐和组态熵的贡献，这是特别重要的在高温下。新方法简单有效，可推广到不同材料和更复杂的液体和缺陷晶体系统。
Free energy calculation is fundamentally important in the research of physics, chemistry, and materials. Thermodynamic integration is the most common way to estimate free energies. In the research, we proposed a unified approach using atomic simulations to calculate the free energies of liquid and defective crystals. The new approach is based on thermodynamic integration using two alchemical pathways. Softcore potentials are developed for three-body interatomic potentials to realize the alchemical pathways. Employing the new approach, the free energy of the liquid can be calculated without requiring another reference system. The free energy of the defective crystal can be calculated directly at high temperatures. It avoids the singularity at the integration endpoint caused by the defect diffusion, which is a serious problem in the widely used Einstein crystal method. In addition, the new approach can capture the whole free energy of the defective crystal including the contribution of anharmonic and configurational entropy, which are particularly important at high temperatures. The new method is simple yet effective and can be extended to different materials and more complex liquid and defective crystal systems.