Stabilizing a molecular switch at solid surfaces: A density functional theory study of azobenzene on Cu(111), Ag(111), and Au(111)
Stabilizing a molecular switch at solid surfaces: A density functional theory study of azobenzene on Cu(111), Ag(111), and Au(111)
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DOI：
10.1103/physrevb.80.035414
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发表时间：
2009-07-01
影响因子：
3.7
通讯作者：
Reuter, Karsten
中科院分区：
文献类型：
--
作者：
McNellis, Erik;Meyer, Joerg;Reuter, Karsten
我们提出了一个密度泛函理论趋势研究，解决了反式顺式构象开关偶氮苯（C6H5-N=N-C6H5）在三个铸币金属表面的结合。根据详细的能量、几何和电子结构数据，我们得出结论，分子-表面相互作用的控制因素是中心偶氮（-N=N-）桥的共价键与两个封闭壳苯基（- c6h5）环的表面相互作用之间的竞争。相对于这个因素，顺式构象表现出更有利的气相几何结构，因此在所研究的表面上更稳定。由于整体结合仍然相当弱，因此两种异构体在Ag（111）和Au（111）处的相对稳定性降低。这在Cu（111）中是明显不同的，在Cu（111）中，顺式键的强度甚至足以在所采用的半局部电子交换和相关（xc）功能的水平上逆转气相的能量顺序。虽然这种实际的逆转很可能受到由于近似xc处理的缺陷的影响，但我们批判性地讨论了表面对亚稳分子状态的一般影响的合理化是相当稳健的。从衍生键机制的角度来看，这同样适用于最近的尖端操纵和光激发异构化实验的分析。
We present a density-functional theory trend study addressing the binding of the trans-cis conformational-switch azobenzene (C6H5-N=N-C6H5) at three coinage-metal surfaces. From the reported detailed energetic-, geometric-, and electronic-structure data we conclude that the governing factor for the molecule-surface interaction is a competition between covalent bonding of the central azo (-N=N-) bridge on the one hand and the surface interaction of the two closed-shell phenyl (-C6H5) rings on the other. With respect to this factor the cis conformer exhibits a more favorable gas-phase geometric structure and is thus more stabilized at the studied surfaces. With the overall binding still rather weak the relative stability of the two isomers is thereby reduced at Ag(111) and Au(111). This is significantly different at Cu(111), where the cis bonding is strong enough to even reverse the gas-phase energetic order at the level of the employed semilocal electronic exchange and correlation (xc) functional. While this actual reversal may well be affected by the deficiencies due to the approximate xc treatment, we critically discuss that the rationalization of the general effect of the surface on the metastable molecular states is quite robust. This should equally hold for the presented analysis of recent tip-manipulation and photoexcitation isomerization experiments from the view point of the derived bonding mechanism.