Ferroelectric surface chemistry: First-principles study of adsorption on the stoichiometric LiNbO3 (0001) surface
Ferroelectric surface chemistry: First-principles study of adsorption on the stoichiometric LiNbO3 (0001) surface
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铁电表面化学：化学计量LiNbO3（0001）表面吸附的第一原理研究
DOI：
10.1103/physrevb.100.245432
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发表时间：
2019
影响因子：
3.7
通讯作者：
Zhu Jinsong
中科院分区：
文献类型：
--
作者：
Yue Chen;Lu Xiaomei;Zhang Junting;Huang Fengzhen;Zhu Jinsong
我们用第一性原理研究了化学计量比{LiNb}{LiNb}{0001]清洁的正负表面，并吸附了羟基和氢原子。虽然我们排除了某些原子物种的浓缩或贫化等内部补偿机制，但在恒定化学计量比的表面弛豫框架下，考虑外来吸附，得到了最低能态的结构。我们发现，正化学计量比表面通过反常的离子位移来补偿表面电荷。我们还认为，外来吸附物质与相反的极性表面处于显著不同的键中，导致了不同的表面电荷补偿机制。水分子吸附在负表面上，甚至会改变表面的极性。讨论了化学计量比极表面的电荷补偿和稳定的五种机制，即吸附原子与表面离子的键合作用、吸附离子的偶极矩、离子位移引起的表面结合电荷的变化、表面自发极化的变化和移动载流子，它们的优先顺序依次为：吸附原子与表面离子的相互作用、吸附离子的偶极矩、离子位移引起的表面结合电荷的变化、表面自发极化的变化和移动载流子。
We present a first-principles study of stoichiometric $\mathrm{LiNb}{\mathrm{O}}_{3}$ (0001) clean positive and negative surface and with ${\mathrm{H}}_{2}\mathrm{O}$, OH and H adsorption. While we exclude internal compensation mechanisms such as enrichment or depletion of certain atomic species, in the frame of surface relaxation with constant stoichiometry and considering the foreign adsorbates, the structures with lowest energy states are obtained. We find that the positive stoichiometric surface compensates the surface charges by abnormal ion displacements. We also suggest that foreign adsorbates are in significantly different bonds with opposite polar surfaces, leading to diverse mechanisms of surface charge compensation. Water molecules adsorbed on negative surface may even alter the surface polarity. We refer to five mechanisms for the charge compensation and the stabilization of stoichiometric polar surfaces, that is, the bonding interaction between adsorbed atoms and surface ions, the dipole moment of adsorbates, the (abnormal) ion displacements-induced change of surface bound charge, the variation of surface spontaneous polarization, and the mobile carriers, with the priority lowering in turn.