标题： NiS_{2-x}Se_x的电子和磁性性质：比较研究 显示英文标题

标题： Electronic and magnetic properties of NiS_{2-x}Se_x: a comparative study

摘要： 金属-绝缘体转变和d电子离域化问题在压力下使用密度泛函理论（DFT）研究了黄铁矿体系NiS_{2-x}Se_x。我们测试了几种近似方法，包括广义梯度近似（GGA）、GGA+U方法和杂化泛函。此外，我们应用了GW近似并进行了哈特里-福克计算。在GGA框架内讨论了硫属二聚体在电子结构中的重要作用，这充分描述了晶格在金属-绝缘体转变中的作用。此外，确定了磁相图。然而，电子性质描述不足——无法获得NiS_2的绝缘基态——并且磁序被略微高估。如果在GGA+U中考虑关联效应，可以找到绝缘体，但掺杂样品的非磁基态不可达。将福克交换与局部近似如GGA混合能够正确再现NiS_2中的绝缘基态以及掺杂和压力下的金属基态。绝缘体——与以前的建议相反——是莫特型的，即间隙在Ni 3d{例子}状态之间打开。由于福克项，磁序被强烈高估。应用的GW计算无法纠正NiS_2的金属特性，并低估了间隙一个数量级。 显示英文摘要

摘要： The metal-insulator transition and the problem of d-electron delocalization are investigated in the pyrite system NiS_{2-x}Se_x under pressure using density functional theory (DFT). We test several approximations, including the generalized gradient approximation (GGA), the GGA+U approach, and hybrid functionals. In addition we apply the GW approximation and perform Hartree-Fock calculations. The important role of the chalcogen dimers in the electronic structure is discussed within GGA, which sufficiently describes the role of the lattice in the metal-insulator transition. In addition, the magnetic phase diagram is determined. However, the electronic properties are inadequately described -- the insulating ground state of NiS_2 cannot be obtained -- and the magnetic order is slightly overestimated. If correlations are taken into account within GGA+U, the insulator is found, but the non-magnetic ground state of the doped samples is not accessible. Mixing Fock exchange with local approximations as GGA correctly reproduce the insulating ground state in NiS_2, and metallic ground states with doping and pressure. The insulator is -- in contrast to earlier suggestions -- of Mott type, i. e. the gap opens between Ni 3d {eg} states. Due to the Fock term, the magnetic order is strongly overestimated. The applied GW calculations are not able to correct the metallic character of NiS_2 and underestimate the gap by one order of magnitude.