First-principles study of the stability of calcium-decorated carbon nanostructures
First-principles study of the stability of calcium-decorated carbon nanostructures
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DOI：
10.1103/physrevb.82.155454
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发表时间：
2010-10
影响因子：
3.7
通讯作者：
C. Cazorla;S. Shevlin;Z. Guo
中科院分区：
文献类型：
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作者：
C. Cazorla;S. Shevlin;Z. Guo
鉴于潜在的生物技术和纳米技术应用对钙修饰碳纳米结构的兴趣，我们对这些体系的能量和结构性质进行了系统和深入的第一性原理计算研究。我们用密度泛函理论(DFT)和从头算分子动力学模拟方法确定了钙修饰石墨烯和碳纳米管(CNT)的最小能量构型、结合能分布和热力学稳定性随掺杂浓度的变化关系。在石墨烯中，我们预测存在一个平衡的(根3 x根3)R30度公度的CaC6单层，它在低温和室温下保持稳定，没有聚集。对于碳纳米管，我们证明了均匀的钙修饰的锯齿形(n<；=10，0)碳纳米管在中等大的掺杂浓度下变得稳定，而钙包覆的扶手椅(n，n)碳纳米管表现出明显的钙聚集的热力学趋势。在钙掺杂的石墨烯和碳纳米管体系中，我们都估计了原子聚集过程的大的能垒(类似于1 eV)，这表明在碳纳米表面上的钙聚集可能受到运动学上的阻碍。最后，通过DFT和Moller-Plesset二阶微扰计算的比较，我们证明DFT大大低估了钙掺杂剂和冠烯分子之间的弱相互作用，并且由于在费米能级附近缺乏电子的pi-d轨道杂化，钙-冠烯体系在物理上不能与钙掺杂的石墨烯相比较。
In view of the interest in calcium-decorated carbon nanostructures motivated by potential biotechnological and nanotechnological applications, we have carried out a systematic and thorough first-principles computational study of the energetic and structural properties of these systems. We use density-functional theory (DFT) and ab initio molecular dynamic simulations to determine minimum energy configurations, binding energy profiles and the thermodynamic stability of Ca-decorated graphene and carbon nanotubes (CNT) as function of doping concentration. In graphene, we predict the existence of an equilibrium (root 3 x root 3) R30 degrees commensurate CaC6 monolayer that remains stable without clustering at low and room temperatures. For carbon nanotubes, we demonstrate that uniformly Ca-decorated zigzag (n <= 10, 0)CNT become stable against clustering at moderately large doping concentrations while Ca-coated armchair (n, n) CNT exhibit a clear thermodynamic tendency for Ca aggregation. In both Ca-doped graphene and CNT systems, we estimate large energy barriers (similar to 1 eV) for atomic aggregation processes, which indicates that Ca clustering in carbon nanosurfaces may be kinematically hindered. Finally, we demonstrate via comparison of DFT and Moller-Plesset second-order perturbation calculations that DFT underestimates significantly the weak interaction between a Ca dopant and a coronene molecule, and also that the Ca-coronene system is not physically comparable to Ca-doped graphene due to lack of electronic pi-d orbitals hybridization near the Fermi energy level.