DFT + \emph{U}的第一性原理研究PbCrO $_{3}$的结构和电子性质
First-principles DFT+\emph{U} study of structural and electronic properties of PbCrO$_{3}$
摘要：
我们对PbCrO $_{3}$、CrPbO $_{3}$以及它们的等比例组合进行了系统的第一性原理研究，计算了它们的结构、电子和磁性。局域密度近似（LDA）$+U$和广义梯度近似$+U$的理论公式已被用来解释强的本地化Cr 3d电子之间的库仑排斥。通过选择Hubbard \emph{U}参数在4 eV左右，可以实现铁磁和/或反铁磁基态，并且我们计算的晶格常数、体模量和状态方程与最近的实验很好地一致[W. Xiao \emph{et al.}，PNAS \textbf{107}，14026（2010）]。这些化合物中的B-$-$-O键具有明显的共价键性质，电子转移研究表明，PbCrO $_{3}$ -CrPbO $_{3}$无规化合物的离子性随CrO $_{6/2}$八面体含量的增加而降低. B-$-$-O键的长度决定了其晶格参数，从而清楚地表明，实验样品中含有CrPbO-$_{3}$以及在压缩时PbO $_{6/2}$八面体向CrO $_{6/2}$的转变是导致体积和压缩性异常增大的原因。
英文摘要：
We have performed a systematic first-principles investigation to calculate the structural, electronic, and magnetic properties of PbCrO$_{3}$, CrPbO$_{3}$ as well as their equiproportional combination. The local density approximation (LDA)$+U$ and the generalized gradient approximation$+U$ theoretical formalisms have been used to account for the strong on-site Coulomb repulsion among the localized Cr 3d electrons. By choosing the Hubbard \emph{U} parameter around 4 eV, ferromagnetic, and/or antiferromagnetic ground states can be achieved and our calculated lattice constants, bulk moduli, and equation of states are in good agreement with recent experiments [W. Xiao \emph{et al.}, PNAS \textbf{107}, 14026 (2010)]. The bonding nature of B$-$O bonds in these ABO$_{3}$ compounds exhibit evident covalent character and our electron transferring study indicates that the ionicity shows decreasing trend with increasing fraction of CrO$_{6/2}$ octahedron within the PbCrO$_{3}$-CrPbO$_{3}$ random compounds. The lengthes of B$-$O bonds determine their lattice parameters, thus, clearly indicates that the abnormally large volume and compressibility is due to the contain of CrPbO$_{3}$ in the experimental sample and the transition of PbO$_{6/2}$ octahedron to CrO$_{6/2}$ upon compression.
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