Galperin M, Beratan D N
Departments of Chemistry and Biochemistry, Duke University, Durham, NC 27708, USA.
J Phys Chem B. 2005 Feb 3;109(4):1473-80. doi: 10.1021/jp045783f.
Scanning tunneling microscope (STM) images of 1,3-cyclohexadiene bound to silicon are interpreted using a nonequilibrium Green's function method. The resolution of the carbon-carbon double bond for positive bias voltages but not for negative bias voltages is explained using a quasiprobability density analysis. The asymmetry in the images arises from the system's voltage dependent electronic structure. A pi* orbital is found to be responsible for the empty state STM images of the carbon-carbon double bond, which is observed experimentally. The pi orbital relevant for the opposite bias does not produce an STM image sharply localized in the bond region because the molecule induces a Si-surface dipole dependent on the bias. The dipole voltage dependence arises from molecular charging. This result emphasizes the importance of simulating the molecule as an element in an open quantum system.
利用非平衡格林函数方法对与硅结合的1,3 - 环己二烯的扫描隧道显微镜（STM）图像进行了解释。通过准概率密度分析解释了正偏压下而非负偏压下碳 - 碳双键的分辨率。图像中的不对称性源于系统与电压相关的电子结构。发现一个π*轨道是碳 - 碳双键空态STM图像的成因，这已通过实验观察到。与相反偏压相关的π轨道不会产生在键区域中尖锐定位的STM图像，因为分子会诱导出一个依赖于偏压的硅表面偶极子。偶极子的电压依赖性源于分子充电。该结果强调了将分子模拟为开放量子系统中的一个元素的重要性。
