论文标题
通过RPA对1D碳链的新见解
New insights into the 1D carbon chain through the RPA
论文作者
论文摘要
我们使用密度函数理论（DFT）和与相关能量的随机相近似（RPA）研究了无限线性碳链（CARBYNE）的电子和结构特性。这些研究是在Vacuo和Carbyne中进行的，在碳纳米管（CNT）内进行。在真空中，半本地DFT和RPA分别预测约0.04Å和0.13Å的键长交替。 $γ$点的最高光学模式的频率为1219 cm $^{ - 1} $，DFT和RPA约为2000 cm $^{ - 1} $。 RPA与先前的高水平量子化学和扩散蒙特卡洛的结果一致。对于RPA，我们计算整个Brillouine区域中的声子 - 分散，并发现与DFT计算的定量差异不仅在$γ$点处，而且在整个Brillouine区域中。为了在碳纳米管内建模Carbyne，我们考虑了A（10,0）CNT。在这里，DFT计算甚至对K点采样敏感。在非常致密的K点采样的石灰下，半本地DFT预测没有键长（BLA），而在RPA中，占0.09Å的较大BLA占上风。降低的BLA导致振动频率的显着红移约为350 cm $^{ - 1} $，因此它们与实验估计值非常吻合。总体而言，RPA与先前报道的相关波函数方法和实验性拉曼数据的良好一致性表明，RPA以中等的计算成本提供了可靠的结果。因此，它为相关波函数方法的曲目提供了有用的补充，其准确性显然是低维系统的占上风，在该系统中，半本地密度函数难以产生甚至定性正确的结果。
We investigated the electronic and structural properties of the infinite linear carbon chain (carbyne) using density functional theory (DFT) and the random phase approximation (RPA) to the correlation energy. The studies are performed in vacuo and for carbyne inside a carbon nano tube (CNT). In the vacuum, semi-local DFT and RPA predict bond length alternations of about 0.04 Å and 0.13 Å, respectively. The frequency of the highest optical mode at the $Γ$ point is 1219 cm$^{-1}$ and about 2000 cm$^{-1}$ for DFT and the RPA. Agreement of the RPA to previous high level quantum chemistry and diffusion Monte-Carlo results is excellent. For the RPA we calculate the phonon-dispersion in the full Brillouine zone and find marked quantitative differences to DFT calculations not only at the $Γ$ point but also throughout the entire Brillouine zone. To model carbyne inside a carbon nanotube, we considered a (10,0) CNT. Here the DFT calculations are even qualitatively sensitive to the k-points sampling. At the limes of a very dense k-points sampling, semi-local DFT predicts no bond length alternation (BLA), whereas in the RPA a sizeable BLA of 0.09 Å prevails. The reduced BLA leads to a significant red shift of the vibrational frequencies of about 350 cm$^{-1}$, so that they are in good agreement with experimental estimates. Overall, the good agreement between the RPA and previously reported results from correlated wavefunction methods and experimental Raman data suggests that the RPA provides reliable results at moderate computational costs. It hence presents a useful addition to the repertoire of correlated wavefunction methods and its accuracy clearly prevails for low dimensional systems, where semi-local density functionals struggle to yield even qualitatively correct results.
