Structure and thermal fluctuation of one-dimensional AgO chains on Ag(110) surfaces studied with density functional theory and Monte Carlo simulations.
Structure and thermal fluctuation of one-dimensional AgO chains on Ag(110) surfaces studied with density functional theory and Monte Carlo simulations.
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DOI：
10.1063/1.2993251
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发表时间：
2008-10
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影响因子：
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通讯作者：
I. Nakai;Y. Matsumoto;N. Takagi;S. Okazaki
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文献类型：
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作者：
I. Nakai;Y. Matsumoto;N. Takagi;S. Okazaki
采用密度泛函理论（DFT）方法研究了Ag（110）表面上AgO连续链和截短链的结构，并用Monte Carlo方法模拟了截短链的热涨落.虽然已知当链在低温下保持线性结构时，CO从一维AgO链中消除氧仅发生在链末端，但链末端的结构尚未被探索。密度泛函理论计算表明，氧封端的链比银封端的链更稳定，并且在费米能级附近有更高的态密度，这与扫描隧道显微镜（STM）的观测结果一致. AgO单元之间的成对相互作用的Monte Carlo模拟再现STM研究中观察到的特征，包括存在的起始温度的链波动和平均链长的氧覆盖率的依赖性。起始温度，一方面，在很大程度上是由平行于链生长的方向上的吸引力相互作用控制的。另一方面，碎片氧化银链的空间分布强烈依赖于在垂直于链的方向上的排斥相互作用。特别是，在垂直于AgO链的方向上的10个单位的晶格常数范围内的排斥相互作用是必不可少的模仿STM观测，其中碎片链几乎保持固有的相互距离的（nx 1）-O相，即使在热波动。
The structures of continuous and truncated AgO chains on Ag(110) surfaces are studied by using density functional theory (DFT) calculations and the thermal fluctuations of truncated chains are simulated by using the Monte Carlo method. Although it is known that oxygen elimination by CO from one-dimensional AgO chains takes place exclusively at chain ends when the chains keep a linear structure at low temperatures, the structure of chain ends has been unexplored. The DFT calculations reveal that oxygen-terminated chains are more stable than silver-terminated ones and have an enhanced density of states near the Fermi level at the terminal oxygen, which is consistent with scanning tunneling microscope (STM) observations. The Monte Carlo simulations with pairwise interactions between AgO units reproduce characteristic features observed in STM studies, including the existence of an onset temperature for the chain fluctuations and the oxygen-coverage dependence of average chain length. The onset temperature, on one hand, is largely controlled by attractive interactions in the direction parallel to chain growth. On the other hand, the spatial distribution of fragmented AgO chains depends strongly on repulsive interactions in the direction perpendicular to chains. In particular, the repulsive interactions ranging ten units of the lattice constant in the direction perpendicular to the AgO chains are essential to mimic STM observations, where fragmented chains almost keep the mutual distance inherent to the (nx1)-O phase even under thermal fluctuations.