LaOFePn体系（Pn =氮族元素）的精细电磁结构
The Delicate Electronic and Magnetic Structure of the LaOFePn System (Pn = pnictogen)
摘要：
高温超导性的发生，以及与磁性的竞争，在化学计量和掺杂的LaOFeAs和同构的铁-氧氮氧化物中提出了许多关于这类材料的电子结构和磁相互作用的基本问题。现在有足够的实验数据，它可能会识别的重要问题，其解决方案将导致理解这个系统。在本文中，我们解决了一些重要的问题。一个重要的特征是铁砷距离（或更抽象的氮族元素（Pn）的高度$z$（Pn）），我们目前的结果$z$（Pn）的电子结构，能量，和Fe磁矩的效果。我们还研究了LaOFeAs在压力下，并调查电子和空穴掺杂的虚晶近似内的效果。的电场梯度的LaOFeAs化合物中的所有原子（未掺杂和掺杂），并与现有的数据进行比较。观测到的$(π,π,π)$磁序进行了研究，并与计算简单的$(π,π,0)$顺序，这可能是一个很好的模型在大多数方面。我们研究了氮族元素原子在这类化合物中的重要作用，并预测了实验上尚未报道的N和Sb对应物的结构和性质。在一定体积下，LaOFeN中费米能级处的间隙打开，将成键带与反键带分开，并为更好地简单理解该系统看似复杂的电子结构提供了方向。最后，我们简要地讨论了后镧稀土的可能影响，已被观察到，以提高超导临界温度显着。
英文摘要：
The occurrence of high temperature superconductivity, and the competition with magnetism, in stoichiometric and doped LaOFeAs and isostructural iron-oxypnictides is raising many fundamental questions about the electronic structure and magnetic interactions in this class of materials. There are now sufficient experimental data that it may be possible to identify the important issues whose resolution will lead to the understanding of this system. In this paper we address a number of the important issues. One important characteristic is the Fe-As distance (or more abstractly the pnictogen (Pn) height $z$(Pn)); we present results for the effect of $z$(Pn) on the electronic structure, energetics, and Fe magnetic moment. We also study LaOFeAs under pressure, and investigate the effects of both electron and hole doping within the virtual crystal approximation. The electric field gradients for all atoms in the LaOFeAs compound are presented (undoped and doped) and compared with available data. The observed $(π,π,π)$ magnetic order is studied and compared with the computationally simpler $(π,π,0)$ order which is probably a very good model in most respects. We investigate the crucial role of the pnictogen atom in this class, and predict the structures and properties of the N and Sb counterparts that have not yet been reported experimentally. At a certain volume a gap opens at the Fermi level in LaOFeN, separating bonding from antibonding bands and suggesting directions for a better simple understanding of the seemingly intricate electronic structure of this system. Finally, we address briefly on the possible effects of post-lanthanum rare earths, which have been observed to enhance the superconducting critical temperature substantially.
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