层状铜氧氯化物[CuCl] LaNb（2）O（7）的结构畸变和磁阻挫相互作用
Structural distortion and frustrated magnetic interactions in the layered copper oxychloride [CuCl]LaNb(2)O(7)
摘要：
我们提出了一个计算研究的层状氯氧化铜[CuCl] LaNb（2）O（7），最近已被提出作为一个自旋1/2挫折正方晶格化合物。我们的研究结果证明了一个轨道简并的基态的四氢呋喃晶体结构，并揭示了一个Jahn-Teller型的结构畸变。这种扭曲严重改变了铜的局部环境--形成CuO（2）Cl（2）斑块而不是CuO（2）Cl（4）八面体--并恢复了氧化铜和卤氧化物典型的单轨道情景。计算的畸变与现有的衍射数据和实验结果的电场梯度的Cu和Cl网站是一致的。能带结构表明了一个复杂的三维自旋模型，相互作用可达第四个邻居。尽管（CuCl）LaNb（2）O（7）具有层状结构，但自旋系统具有明显的一维特征。然而，相当大的链间相互作用导致强烈的挫折，并可能导致自旋隙行为。个别交换耦合的计算估计与实验数据定性一致。
英文摘要：
We present a computational study of the layered copper oxychloride [CuCl]LaNb(2)O(7) that has been recently proposed as a spin-1/2 frustrated square lattice compound. Our results evidence an orbitally degenerate ground state for the reported tetragonal crystal structure and reveal a Jahn-Teller-type structural distortion. This distortion heavily changes the local environment of copper -- CuO(2)Cl(2) plaquettes are formed instead of CuO(2)Cl(4) octahedra -- and restores the single-orbital scenario typical for copper oxides and oxyhalides. The calculated distortion is consistent with the available diffraction data and the experimental results on the electric field gradients for the Cu and Cl sites. The band structure suggests a complex three-dimensional spin model with the interactions up to the fourth neighbors. Despite the layered structure of (CuCl)LaNb(2)O(7), the spin system has pronounced one-dimensional features. Yet, sizable interchain interactions lead to the strong frustration and likely cause the spin-gap behavior. Computational estimates of individual exchange couplings are in qualitative agreement with the experimental data.
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