Wolff Holger, Dronskowski Richard
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany.
J Comput Chem. 2008 Oct;29(13):2260-7. doi: 10.1002/jcc.20895.
A series of perovskite-type phases of alkaline-earth-based tantalum and niobium oxynitrides has been studied using both first-principles electronic-structure calculations and molecular-dynamics simulations, in particular by investigating different structural arrangements and anion distributions in terms of total-energy calculations. The structural properties are explained on the basis of COHP chemical bonding analyses and semiempirical molecular orbital calculations. We provide theoretical proof for the surprising result that the local site symmetries of these phases are lower than cubic because density-functional calculations clearly show that all crystallographic unit cells are better described as being orthorhombic with space group Pmc2(1) to optimize metal-nitrogen bonding; nonetheless, there is no contradiction with a macroscopic cubic description of the structures of BaTaO(2)N and BaNbO(2)N adopting space group Pm3m. Additionally, we find that the anionic sublattice is ordered in all compounds studied over a wide temperature range.
利用第一性原理电子结构计算和分子动力学模拟，对一系列碱土基金属钽和铌的氧氮化物钙钛矿型相进行了研究，特别是通过总能计算研究了不同的结构排列和阴离子分布。基于COHP化学键分析和半经验分子轨道计算对结构性质进行了解释。我们为这些相的局域位点对称性低于立方对称性这一惊人结果提供了理论证据，因为密度泛函计算清楚地表明，所有晶体学晶胞更好地描述为正交晶系，空间群为Pmc2(1)，以优化金属-氮键；然而，这与采用空间群Pm3m的BaTaO(2)N和BaNbO(2)N结构的宏观立方描述并不矛盾。此外，我们发现，在所研究的所有化合物中，阴离子亚晶格在很宽的温度范围内都是有序的。
