Liu Hongmei, Wang Nan, Zhao Jianwei, Guo Yan, Yin Xing, Boey Freddy Y C, Zhang Hua
Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008, PR China.
Chemphyschem. 2008 Jul 14;9(10):1416-24. doi: 10.1002/cphc.200800032.
Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.
分子导线通过在两端用-SH基团进行功能化，与金电极共价键合，形成金属-分子-金属结。利用第一性原理密度泛函理论（DFT）结合非平衡格林函数（NEGF）形式，从理论上研究了各种分子结的电导。基于一系列分子导线的链长依赖性电导，获得了衰减因子β，并与实验数据进行了比较。β值与分子的最高占据分子轨道（HOMO）-最低未占据分子轨道（LUMO）能隙定量相关。金属电极与分子桥之间的耦合在电子输运中起着重要作用。通过将分子桥长度外推至零，得到了6.0±2.0千欧的接触电阻。该值与量子电阻大小相同。
