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Orbital ordering, ferroelasticity, and the large pressure-induced volume collapse in PbCrO_3

机译:PbCrO_3的轨道有序性,铁弹性和大压力诱发的体积塌陷

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We predict a tetragonal ground state for perovskite-structured PbCrO_3 from density functional theory (DFT) + U calculations, and explain its anomalously large volume. The predicted structure is stabilized due to orbital ordering of Cr d in the presence of a large tetragonal crystal field, mainly due to off-centering of the Pb atom. At higher pressures (smaller volumes) there is a first-order transition to a cubic phase where the Cx-d orbitals are orbitally liquid. This phase transition is accompanied by a ~11.5% volume collapse, one of the largest known for transition-metal oxides. The large ferroelasticity and its strong coupling to the orbital degrees of freedom could be exploited to form potentially useful magnetostrictive materials.
机译:我们根据密度泛函理论(DFT)+ U计算预测了钙钛矿结构的PbCrO_3的四方基态,并解释了其异常大的体积。在大四方晶场的存在下,由于Cr d的轨道有序化,主要是由于Pb原子的偏心化,因此预测的结构得以稳定。在较高的压力(较小的体积)下,会发生一阶过渡到立方相的过程,其中Cx-d轨道在轨道上是液态的。这种相变伴随着〜11.5%的体积塌陷,这是已知的最大的过渡金属氧化物之一。可以利用大的铁弹性及其与轨道自由度的强耦合来形成潜在有用的磁致伸缩材料。

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