Silva Nadeesha J, Machado Francisco B C, Lischka Hans, Aquino Adelia J A
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock Texas 79409, USA.
Departamento de Química, Instituto Tecnológico de Aeronáutica, São José dos Campos, 12.228-900 São Paulo, Brazil.
Phys Chem Chem Phys. 2016 Aug 10;18(32):22300-10. doi: 10.1039/c6cp03749f.
High level ab initio calculations ranging from coupled cluster methods including explicitly correlated approaches to standard second order Møller-Plesset theory using spin scaling (SOS-MP2) have been performed on sandwich and slipped parallel dimer structures of a series of quasi one-dimensional acenes and on two-dimensional sheets containing the pyrene to coronene series encircled with two layers of benzene rings. Sandwich (graphitic AA type) and slipped parallel (AB type) structures were considered and, within the given symmetry restrictions, full geometry optimizations were performed. Basis set superposition effects have been considered. The computed geometries show a significant biconcave deviation of the two-dimensional sheets from planarity with the central intersheet CC distances considerably smaller that van der Waals distances. The computed intersheet binding energy per carbon atom extrapolated for N → ∞ of -74.3 meV (1.713 kcal mol(-1)) per atom agrees quite well with an experimental defoliation energy of -52 meV (1.199 kcal mol(-1)) per atom (-67 meV (1.545 kcal mol(-1)) per carbon atom without corrections for H binding contributions) for polyaromatic hydrocarbons (PAHs) from graphite. A limited investigation of density functional theory (DFT) calculations using empirical dispersion contributions has been performed also showing a significant underbinding character of the D3 method. For most of the DFT variants investigated the graphene sheet models retain a quasi-planar structure in strong contrast to the aforementioned SOS-MP2 results.
我们对一系列准一维并苯的夹心和平行错位二聚体结构，以及包含芘到 coronene 系列且被两层苯环环绕的二维片层进行了高水平的从头算计算，计算方法涵盖了从包含显式相关方法的耦合簇方法到使用自旋标度的标准二阶 Møller-Plesset 理论（SOS-MP2）。考虑了夹心（石墨 AA 型）和平行错位（AB 型）结构，并在给定的对称性限制内进行了完全几何优化。考虑了基组叠加效应。计算得到的几何结构表明，二维片层与平面存在显著的双凹偏差，中心层间 CC 距离远小于范德华距离。计算得到的每个碳原子的层间结合能在 N → ∞ 时外推为 -74.3 meV（1.713 kcal mol⁻¹）/原子，这与石墨中多环芳烃（PAHs）的实验脱叶能 -52 meV（1.199 kcal mol⁻¹）/原子（未校正 H 结合贡献时为 -67 meV（1.545 kcal mol⁻¹）/碳原子）相当吻合。还进行了有限的使用经验色散贡献的密度泛函理论（DFT）计算研究，结果也表明 D3 方法存在显著的结合不足特征。对于所研究的大多数 DFT 变体，石墨烯片层模型保持准平面结构这与上述 SOS-MP2 结果形成强烈对比。
