涂抹法和四面体法的有效性：DFT规范中的最佳实践
Effectiveness of smearing and tetrahedron methods: best practices in DFT codes
摘要：
密度泛函理论（DFT）代码在材料的高通量筛选中通常被视为“黑盒”，用户选择输入参数的默认值。通常，非专家可能无法充分考虑这些参数对预测质量的影响。在这项工作中，我们试图确定一个强大的参数集相关的涂抹和四面体的方法，返回各种金属系统的数值准确和有效的结果。在两个流行的DFT代码：维也纳从头算模拟包（VASP）和量子浓缩（QE）的涂抹和四面体方法的总能量，自洽场周期的数量，和原子上的力的影响进行了研究。从近40，000次计算中可以明显看出，最佳涂抹取决于系统、涂抹方法、涂抹参数和$k$点密度。涂抹的益处是自洽场循环的数量的轻微减少，这与涂抹方法或参数无关。一个大的涂抹参数--被认为是大的是系统相关的--导致不准确的总能量和力。Blöchl的四面体方法导致总能量的小改进。当用相同的输入参数处理不同的系统时，我们建议使用尽可能少的拖尾，因为拖尾的系统依赖性和选择一个参数，给出不准确的能量和力的风险。
英文摘要：
Density functional theory (DFT) codes are commonly treated as a "black box" in high-throughput screening of materials, with users opting for the default values of the input parameters. Often, non-experts may not sufficiently consider the effect of these parameters on prediction quality. In this work, we attempt to identify a robust set of parameters related to smearing and tetrahedron methods that return numerically accurate and efficient results for a wide variety of metallic systems. The effects of smearing and tetrahedron methods on the total energy, number of self-consistent field cycles, and forces on atoms are studied in two popular DFT codes: the Vienna Ab initio Simulation Package (VASP) and Quantum Espresso (QE). From nearly 40,000 computations, it is apparent that the optimal smearing depends on the system, smearing method, smearing parameter, and $k$-point density. The benefit of smearing is a minor reduction in the number of self-consistent field cycles, which is independent of the smearing method or parameter. A large smearing parameter -- what is considered large is system dependent -- leads to inaccurate total energies and forces. Blöchl's tetrahedron method leads to small improvements in total energies. When treating diverse systems with the same input parameters, we suggest using as little smearing as possible due to the system dependence of smearing and the risk of selecting a parameter that gives inaccurate energies and forces.
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