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Multicenter Bonding Effects in Oxygen Vacancy in the Bulk and on the Surface of MgO
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-05-11 00:00:00 , DOI: 10.1021/acs.jpcc.8b03118
Ivan A. Popov 1 , Elisa Jimenez-Izal 2, 3 , Anastassia N. Alexandrova 2, 4 , Alexander I. Boldyrev 1
Affiliation  

We have studied the electronic structure of F-centers in the bulk and on the (100) surface of the MgO crystal. Chemical bonding analysis was performed using the natural bond orbital (NBO) analysis with periodic boundary conditions and the solid state adaptive natural density partitioning (SSAdNDP) method. The bonding in the pristine MgO was found to be very ionic, i.e., there are four lone pairs (s-, px-, py-, and pz-type) on every oxygen atom with the occupation numbers (ONs) in the range of 1.76–1.86 |e|. Within the O vacancy (Ov) located in the bulk of MgO we found a pair of electrons in the place of the missing oxygen atom that is revealed by SSAdNDP as a six-center two-electron (6c–2e) σ bond delocalized over six Mg atoms with ON = 1.87 |e|. In the other defected MgO system featuring the Ov on the (100) surface we also found a pair of electrons in the place of the missing oxygen atom that is revealed as a 5c–2e σ bond with ON = 1.84 |e|. Inclusion of the four closest Mg atoms of the second layer increases the ON value of this bond to 1.91 |e|. We believe that the SSAdNDP method has a great potential for the analysis of chemical bonding of surface atoms, bulk and surface defects, ad-atoms, as well as at interfaces.

中文翻译:

MgO本体和表面氧空位的多中心键合效应

我们已经研究了MgO晶体的主体和(100)表面中F中心的电子结构。使用具有周期性边界条件的自然键轨道(NBO)分析和固态自适应自然密度分配(SSAdNDP)方法进行化学键分析。在原始的MgO的结合被发现是非常离子的,即,有四个孤对(S-,P X - ,P ÿ -和p Ž型)上,在占有数(ONS)每氧原子1.76–1.86的范围| e |。在O空缺(O v)位于大量的MgO中,我们发现了一对电子代替失落的氧原子,这由SSAdNDP揭示为六个中心的两个电子(6c–2e)σ键在6个Mg原子上偏心,且ON = 1.87 | e |。在另一个在(100)表面具有O v的有缺陷的MgO系统中,我们还发现了一对电子,代替了缺失的氧原子,显示为5c–2eσ键,ON = 1.84 |。e |。包含第二层的四个最接近的Mg原子可使该键的ON值增加至1.91 | e |。我们认为,SSAdNDP方法在分析表面原子,整体和表面缺陷,ad原子以及界面的化学键合方面具有巨大的潜力。
更新日期:2018-05-11
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