Nemrava Sandra, Vinnik Denis A, Hu Zhiwei, Valldor Martin, Kuo Chang-Yang, Zherebtsov Dmitry A, Gudkova Svetlana A, Chen Chien-Te, Tjeng Liu Hao, Niewa Rainer
University of Stuttgart , Stuttgart 70049, Germany.
South Ural State University , Chelyabinsk 454080, Russia.
Inorg Chem. 2017 Apr 3;56(7):3861-3866. doi: 10.1021/acs.inorgchem.6b02688. Epub 2017 Mar 14.
The coexistence of three valence states of Mn ions, namely, +2, +3, and +4, in substituted magnetoplumbite-type BaFeMnO was observed by soft X-ray absorption spectroscopy at the Mn-L edge. We infer that the occurrence of multiple valence states of Mn situated in the pristine purely iron(III) compound BaFeO is made possible by the fact that the charge disproportionation of Mn into Mn and Mn requires less energy than that of Fe into Fe and Fe, related to the smaller effective Coulomb interaction of Mn (d) compared to Fe (d). The different chemical environments determine the location of the differently charged ions: with Mn occupying positions with (distorted) octahedral local symmetry, Mn ions prefer octahedrally coordinated sites in order to optimize their covalent bonding. Larger and more ionic bonded Mn ions with a spherical charge distribution accumulate at tetrahedrally coordinated sites. Simulations of the experimental Mn-L XAS spectra of two different samples with x = 1.5 and x = 1.7 led to Mn:Mn:Mn atomic ratios of 0.16:0.51:0.33 and 0.19:0.57:0.24.
通过软X射线吸收光谱法在Mn-L边缘观察到取代磁铅石型BaFeMnO中Mn离子的三种价态，即+2、+3和+4共存。我们推断，在原始纯铁（III）化合物BaFeO中Mn出现多种价态是因为与Fe（d）相比，Mn（d）的有效库仑相互作用较小，Mn电荷歧化为Mn和Mn所需的能量比Fe歧化为Fe和Fe所需的能量少。不同的化学环境决定了不同电荷离子的位置：Mn占据（扭曲）八面体局部对称性的位置，Mn离子倾向于八面体配位位点以优化其共价键。具有球形电荷分布的更大且离子键更强的Mn离子聚集在四面体配位位点。对x = 1.5和x = 1.7的两个不同样品的实验Mn-L XAS光谱进行模拟，得到Mn:Mn:Mn原子比为0.16:0.51:0.33和0.19:0.57:0.24。
