Structure and ordering of oxygen on unreconstructed Ir(100)
Structure and ordering of oxygen on unreconstructed Ir(100)
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DOI：
10.1103/physrevb.93.235406
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发表时间：
2016-06-03
影响因子：
3.7
通讯作者：
Mueller, S.
中科院分区：
文献类型：
--
作者：
Ferstl, P.;Schmitt, T.;Mueller, S.
通过低能电子衍射（LEED）、扫描隧道显微镜（STM）和密度泛函理论（DFT）等实验和理论方法相结合，研究了氧在未重构的Ir（100）表面的吸附。在180 K以下，除了已知的（2 x 1）-O相外，还发现了一个新的（3 x 1）-O相。我们的DFT计算预测这两个阶段是唯一的基本基态的系统中的覆盖范围高达0.5单层。作为覆盖率的函数的相变的分析揭示了清洁表面和3 X 1相之间或3 X 1和2 X 1相之间的扩展共存范围。作为温度的函数，这两个相在约650 K的2 × 1相和180 K的3 × 1相进行有序-无序转变，后者仅部分可逆。用密度泛函理论计算的模型缺陷结构的能量可以一致地解释这种完全有序化行为。的晶体结构的阶段是由全动态LEED强度分析，实验和计算数据集之间产生良好的协议（彭德里R-因子：R-P近似为0.1）。氧被发现承担桥梁网站总是引起显着的弛豫基板内。推导出的结构参数与皮米尺度上DFT的相应预测相吻合。它还表明，残留物和前体阶段的清洁表面的重建只能通过应用程序的实空间的方法，如STM检测。本研究的首要目标是展示如何精确和准确地这样的吸附系统可以通过使用一致的实验和理论方法进行研究。
The adsorption of oxygen on the unreconstructed Ir(100) surface is investigated by a combination of experimental and theoretical methods comprising low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density-functional theory (DFT). Apart from the well-known (2 x 1)-O phase, we find a new (3 x 1)-O phase for temperatures below 180 K. Our DFT calculations predict these two phases to be the only fundamental ground states of the system in the coverage range up to 0.5 monolayers. An analysis of the phase transitions as a function of coverage reveals extended coexistence ranges between the clean surface and the 3 x 1 phase, or between the 3 x 1 and 2 x 1 phases, respectively. As a function of temperature, both phases undergo order-disorder transitions at about 650 K for the 2 x 1 phase and 180 K for the 3 x 1 phase, the latter being only partially reversible. The complete ordering behavior can be consistently explained by the energetics of model defect structures calculated by DFT. The crystallographic structure of the phases is determined by full-dynamical LEED intensity analyses, yielding excellent agreement between experimental and calculated data sets (Pendry R-factors: R-P approximate to 0.1). Oxygen was found to assume bridge sites always inducing significant relaxations within the substrate. The derived structural parameters coincide with the respective predictions from DFT on the picometer scale. It is also shown that remnants and precursor stages of the clean surface's reconstruction can only be detected through the application of real-space methods such as STM. The overarching objective of the present study is to demonstrate how precisely and accurately such an adsorption system can be investigated nowadays by using a concerted experimental and theoretical approach.