Status of free-energy representations for the homogeneous electron gas
Status of free-energy representations for the homogeneous electron gas
复制标题
DOI：
10.1103/physrevb.99.195134
复制
发表时间：
2019-05
影响因子：
3.7
通讯作者：
V. Karasiev;S. Trickey;J. Dufty
中科院分区：
文献类型：
--
作者：
V. Karasiev;S. Trickey;J. Dufty
最近对均匀电子气（HEG）在很宽的密度和温度范围内的精确模拟激发了人们对它的新兴趣。这些数据，结合已知的理论极限，导致自由能的解析表示。这样的表示至少在原理上是完整的HEG状态方程。这里的初始目标是建立两个最佳表示[“corrKSDT，”Phys.Rev.Lett. 112，076403（2014），Phys.Rev.Lett. 120，076401（2018）和“GDB”Phys.Rev.Lett. 119，135001（2017）]的模拟数据和约束在函数形式和表示的准确性方面实际上是相同的。第二个目的是揭示和描述一个重大的困难。尽管他们预期的自由能的准确性，基本的功能形式是不够的推导出的热力学性质。作为一个例子，从表示获得的比热表现出异常，表明需要首先在临界状态下的额外的模拟数据，然后为精细的拟合函数。然而，现有的表示几乎肯定足以用于仅基于自由能的应用（例如，热稠密物质的密度泛函理论）。第三个目标是表明，尽管他们无法提供一个完整的热力学描述的HEG，最好的分析表示提供了一个完全足够的交换相关局部密度近似的自由能密度泛函计算。
Renewed interest in the homogeneous electron gas (HEG) has been stimulated by recent accurate simulations of it over a wide range of densities and temperatures. Those data, combined with known theoretical limits, have led to analytical representations of the free energy. Such a representation is, at least in principle, the complete HEG equation of state. The initial objective here is to establish that the two best representations [“corrKSDT,” Phys. Rev. Lett. 112, 076403 (2014), Phys. Rev. Lett. 120, 076401 (2018), and “GDB” Phys. Rev. Lett. 119, 135001 (2017)] of the simulation data and constraints are effectively the same in both functional form and accuracy of representation. The second objective is to disclose and delineate a significant difficulty. Despite their expected accuracy for the free energy, the underlying functional form is not adequate for derived thermodynamic properties. As an example, the specific heats obtained from the representations exhibit anomalies suggesting the need first for additional simulation data in critical regimes, then for refined fitting functions. The existing representations are, however, almost certainly adequate for applications based on the free energy alone (e.g., density-functional theory for warm dense matter). The third objective is to show that, despite their inability to provide a complete thermodynamic description of the HEG, the best analytical representations do provide a fully adequate exchange-correlation local density approximation for free-energy density-functional calculations.