结晶苯低压phase diagram的量子Monte Carlo模拟
Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo
摘要：
本文采用量子蒙特卡罗（QMC）和密度泛函理论（DFT）方法研究了低压（0 ~ 10 GPa）下结晶苯的相图。我们认为$Pbca$、$P4_32_12$和$P2_1/c$结构是I期和II期的最佳候选结构。我们进行扩散量子蒙特卡罗（DMC）计算，以获得准确的静态相图作为现代范德华密度泛函的基准。我们使用密度泛函微扰理论计算声子的贡献的自由能计算。我们的密度泛函压力相图表明，$Pbca$和$P2_1/c$结构是最稳定的相在所研究的压力范围内。DMC吉布斯自由能计算预测，室温下$Pbca$到$P2_1/c$相变发生在2.1（1）GPa。这一预测与室温下的实验结果一致。我们的DMC计算表明，结晶苯晶格能的估计值为50.6 $\pm$ 0.5 kJ/mol。
英文摘要：
We study the low-pressure (0 to 10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo (QMC) and density functional theory (DFT) methods. We consider the $Pbca$, $P4_32_12$, and $P2_1/c$ structures as the best candidates for phase I and phase II. We perform diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. We use density functional perturbation theory to compute phonon contribution in the free-energy calculations. Our DFT enthalpy-pressure phase diagram indicates that the $Pbca$ and $P2_1/c$ structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature $Pbca$ to $P2_1/c$ phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations show an estimate of 50.6$\pm$0.5 kJ/mol for crystalline benzene lattice energy.
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