Cu(100)表面c(2×2)-N原子结构与吸附行为研究

用密度泛函理论的总能计算研究了金属铜(100)面的表面原子结构以及氮原子的c(2×2)吸附状态.研究结果表明：在Cu(100) c(2×2)-N表面系统中，氮原子处于四度配位的空洞(FFH)位置，距离最表面铜原子层的垂直距离为0.20?，最短的Cu—N键长度为1.83?.结构优化的计算否定了被吸附物导致的表面再构模型，即c(2×2)元胞的两个铜原子在垂直于表面方向发生相对位移，一个铜原子运动到氮原子之上的模型.该吸附表面的功函数约为4.65eV, 氮原子的平均吸附能为4.92 eV(以孤立氮原子为能量参考点).计算结果还说明，Cu—N杂化形成的表面局域态的位置在费米面以下约1.0 eV附近出现，氮原子和第一层以及第二层铜原子均有不同程度的杂化作用.该结果为最近有关该表面的STM图像的争论提供了判据性的第一性原理计算结果. 关键词： Cu(100) c(2×2)-N 表面吸附态 密度泛函总能计算

DFT total energy study on the atomic geometry and adsorption of Cu(100) c(2 × 2)-N surface

We have performed total energy calculations on the structural and adsorption properties of Cu(100) c(2×2)-N surface by using DFT PAW method. It is concluded that nitrogen adsorbed on a four-fold coordinated site with a perpendicular distance of 0.2? from the surface Cu layer. The shortest Cu-N bond length is calculated to be 1.83?. Geometry optimization calculation excludes the possibilities of adsorbate induced reconstruction mode suggested by Driver and Woodruff and the atop model. The simulated work function for this absorbate-substrate system is 4.65 eV which is quite close to that on the clean Cu(100) surface. The total energy calculations showed that the average adsorption energy per nitrogen atom in the case of Cu(100) c(2×2)-N is about 4.92 eV with respect to a solitude N atom. The absorption of nitrogen on the Cu(100) surface yields the hybridization between surface Cu and N atoms, and generates the localized surface states at -1.0 eV relative to Fermi energy E_F. The present study provides a strong criterion to account for the argument on the scanning tunneling microscopy(STM) images from different research groups.
Keywords： Cu(100) c(2×2)-N surface adsorption state total energy calculation