钒氧酞菁(VOPc)与钒酞菁(VPc)分子的扫描隧道显微镜图像模拟

利用第一性原理方法模拟了自由钒氧酞菁(VOPc)和钒酞菁(VPc)分子的扫描隧道显微镜(STM)图像,与实验观察结果相当符合.理论STM图像都显示出亚分子内结构,外围呈四叶状.其主要差异表现在VOPc分子中心处的钒氧离子在STM图像中为一空洞,而在VPc分子的STM图像中钒离子为突起的亮斑.通过分析VOPc和VPc分子的电子结构,对模拟结果给出自洽的理论解释.造成两者图像显著不同的物理原因是VPc分子在费米能级附近有明显含dz2成分的分子轨道,导致钒离子在STM图像中央为突起的亮斑.而在VOPc分子中dz2分态密度峰位由于氧原子的加入使之远离费米能级,使STM不能“看到”VOPc分子中钒氧离子.关键词：钒氧酞菁钒酞菁STM图像模拟电子结构

Simulations of scanning tunneling microscope images for vanadyl phthalocyanine (VOPc) and vanadium phthalocyanine (VPc)

We presented the simulated scanning tunneling microscope (STM) images of vanadyl phthalocyanine (VOPc) and vanadium phthalocyanine (VPc) molecules as well as their electronic structures obtained by using the first-principles method. The simulated STM images show submolecular structures and four-leaves at its periphery, and well reproduce the features of the experimental images. The main difference between the two molecules is that the central vanadium ion in VPc appears as a bright bump in the molecular image, while there is a hole at the centre of the molecular STM image in VOPc. The simulated images are interpreted by that VPc molecule has significant d z 2 character near the Fermi level, while the dark central region is attributed to the oxygen atom causing the d z 2 states far away from Fermi level in VOPc molecule.