Stølen Svein, Mohn Chris E, Ravindran P, Allan Neil L
Department of Chemistry and Centre for Nanotechnology and Materials Science, University of Oslo, Postbox 1033 Blindern, N0315 Oslo, Norway.
J Phys Chem B. 2005 Jun 30;109(25):12362-5. doi: 10.1021/jp050697g.
We discuss the importance of the topography of the potential energy hypersurface for the ionic conductivity of perovskite-related A(2)B(2)O(5) oxides. A correlation between the energetic preference of the cations for different coordination geometries and the ionic conductivity is proposed based on a first principles periodic density functional theory study of selected possible structures for Ba(2)In(2)O(5), Sr(2)Fe(2)O(5), Sr(2)Mn(2)O(5), and La(2)Ni(2)O(5). There are a large number of low-energy local minima on the potential energy hypersurfaces of the two first compounds due to an energetic preference for BO(4) tetrahedra. Tetrahedral environments are energetically unfavorable for Mn(III) in Sr(2)Mn(2)O(5) and for Ni(II) in La(2)Ni(2)O(5), and the number of low-energy configurations is relatively low in these two cases. Consistent with our findings, in contrast to Sr(2)Fe(2)O(5) and Ba(2)In(2)O(5), Sr(2)Mn(2)O(5) and La(2)Ni(2)O(5) do not exhibit transitions to disordered phases on heating, and there appear to be no reports of enhanced ionic conductivity for these compounds. Thus we suggest that the possibility of many different oxygen orderings associated with a variety of low-energy connectivity schemes within tetrahedral layers such as in the brownmillerite-based structures of Sr(2)Fe(2)O(5) and Ba(2)In(2)O(5) is a prerequisite for high ionic conductivity in perovskite-related A(2)B(2)O(5) oxides.
我们讨论了势能超曲面的拓扑结构对钙钛矿相关的A(2)B(2)O(5)氧化物离子电导率的重要性。基于对Ba(2)In(2)O(5)、Sr(2)Fe(2)O(5)、Sr(2)Mn(2)O(5)和La(2)Ni(2)O(5)的选定可能结构进行的第一性原理周期性密度泛函理论研究，提出了阳离子对不同配位几何结构的能量偏好与离子电导率之间的相关性。由于对BO(4)四面体的能量偏好，前两种化合物的势能超曲面上存在大量低能量局部极小值。四面体环境在能量上对Sr(2)Mn(2)O(5)中的Mn(III)和La(2)Ni(2)O(5)中的Ni(II)不利，在这两种情况下低能量构型的数量相对较少。与我们的发现一致，与Sr(2)Fe(2)O(5)和Ba(2)In(2)O(5)相反，Sr(2)Mn(2)O(5)和La(2)Ni(2)O(5)在加热时不会转变为无序相，并且似乎没有关于这些化合物离子电导率增强的报道。因此，我们认为，与四面体层内多种低能量连接方案相关的许多不同氧有序排列的可能性，如在Sr(2)Fe(2)O(5)和Ba(2)In(2)O(5)的钙钛矿相关A(2)B(2)O(5)氧化物中，是高离子电导率的先决条件。
