论文标题
单原子厚金属氮化金属CRN $ _4 $的预测，带有方形平面网络和高温铁磁
Prediction of single-atom-thick transition metal nitride CrN$_4$ with a square-planar network and high-temperature ferromagnetism
论文作者
论文摘要
单原子厚的二维材料（例如石墨烯）通常具有六边形晶格，而方形晶格在二维材料家族中并不常见。在这里，我们证明了单原子过渡金属氮化金属CRN $ _4 $单层是具有方形平面网络的稳定的独立式层。 方平面几何形状的稳定性归因于N = N双键，CR-N协调键和$π$ -D的偶联的组合，其中在先前的研究中很少报道双重$π$ -D共轭。 与合成的G-C $ _3 $ n $ _4 $单层相比，这种机制与报告的二维材料完全不同，从而导致较低的地层能量和更强的稳定性。 另一方面，CRN $ _4 $ layer具有铁磁基态，其中两个Cr原子之间的铁磁耦合是由$π$ -D结合的半填充大$π$轨道的电子介导的。 CRN $ _4 $单层中的高温铁磁性通过使用Monte Carlo方法求解Heisenberg模型来确认。
Single-atom-thick two-dimensional materials such as graphene usually have a hexagonal lattice while the square-planar lattice is uncommon in the family of two-dimensional materials. Here, we demonstrate that single-atom-thick transition metal nitride CrN$_4$ monolayer is a stable free-standing layer with a square-planar network. The stability of square-planar geometry is ascribed to the combination of N=N double bond, Cr-N coordination bond, and $π$-d conjugation, in which the double $π$-d conjugation is rarely reported in previous studies. This mechanism is entirely different from that of the reported two-dimensional materials, leading to lower formation energy and more robust stability compared to the synthesized g-C$_3$N$_4$ monolayer. On the other hand, CrN$_4$ layer has a ferromagnetic ground state, in which the ferromagnetic coupling between two Cr atoms is mediated by electrons of the half-filled large $π$ orbitals from $π$-d conjugation. The high-temperature ferromagnetism in CrN$_4$ monolayer is confirmed by solving the Heisenberg model with Monte Carlo method.
