无缺陷单晶石墨的面间刚度
Interplanar stiffness in defect-free monocrystalline graphite
摘要：
由于范德华相互作用的贡献，石墨中的面间键强度已被确定为非常低。然而，在这项研究中，我们使用微观皮秒超声证明，弹性常数，$C_{33}$，沿$c$轴的无缺陷的单晶石墨超过45 GPa，这是高于20%的报道值。现有的理论不能再现这种强相关的面间系统，我们的结果，因此，表明改进的必要性。由于LDA+U+RPA方法，包括随机相位近似关联和$p$ Wannier轨道的短程关联，比LDA甚至比ACFDT-RPA方法更符合观测，实验结果表明电子关联效应对短程和长程相互作用都不可忽略.
英文摘要：
The interplanar bond strength in graphite has been identified to be very low owing to the contribution of the van der Waals interaction. However, in this study, we use microscopic picosecond ultrasound to demonstrate that the elastic constant, $C_{33}$, along the $c$ axis of defect-free monocrystalline graphite exceeds 45 GPa, which is higher than reported values by 20\%. Existing theories fail to reproduce this strongly correlated interplanar system, and our results, thus, indicate the necessity for improvement. Since the LDA+U+RPA method, including both random phase approximation correlation and short-range correlation in $p$ Wannier orbitals, shows better agreement with the observation than LDA or even than ACFDT-RPA, the experimental results indicate non-negligible electron correlation effects with respect to both the short-range and long-range interactions.
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