Zhang Ruiqi, Hu Zhenpeng, Li Bin, Yang Jinlong
Hefei National Laboratory for Physics at Microscale and ‡Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
J Phys Chem A. 2014 Oct 2;118(39):8953-9. doi: 10.1021/jp5018218. Epub 2014 Apr 17.
On the basis of Bardeen's perturbation theory on electron tunneling and inspired by Paz et al.'s study, a new expression for the tunneling current between the scanning tunneling microscopy (STM) tip and sample has been obtained, and it provides us with an efficient method to simulate STM images. The method can be implemented in any code of first-principles computing software, which offers the wave functions of the tip and sample, calculated independently at the same footing, as input. By calculating the integral with fast Fourier transform (FFT), simulating the STM image of a given sample surface by a database of different tips on a PC turns out to be not a time-consuming work. Compared with Paz et al.'s method, our method abandons the application of the vacuum Green function and possesses better computing efficiency, fewer parameters, and more reasonable simulated results especially at lower computing cost. Simple tip-sample systems, such as H-H and Pd2-Ag2, are taken as benchmarks to test our method. The topographic images of a CO molecule adsorbed on a Cu(111) surface obtained by using a tungsten tip and a CO-terminated tip are also simulated, and the simulated results are in good agreement with the experimental ones.
基于巴丁关于电子隧穿的微扰理论，并受帕兹等人研究的启发，得到了扫描隧道显微镜（STM）针尖与样品之间隧穿电流的新表达式，这为我们提供了一种模拟STM图像的有效方法。该方法可在任何第一性原理计算软件代码中实现，这些软件提供针尖和样品的波函数，且它们在相同基础上独立计算后作为输入。通过用快速傅里叶变换（FFT）计算积分，在个人电脑上利用不同针尖的数据库模拟给定样品表面的STM图像并非一项耗时的工作。与帕兹等人的方法相比，我们的方法摒弃了真空格林函数的应用，具有更好的计算效率、更少的参数，尤其是在较低计算成本下能得到更合理的模拟结果。以简单的针尖 - 样品体系，如H - H和Pd2 - Ag2作为基准来测试我们的方法。还模拟了使用钨针尖和CO端接针尖获得的吸附在Cu(111)表面的CO分子的形貌图像，模拟结果与实验结果吻合良好。
