Kitaev exchange, a new paradigm in quantum magnetism research, occurs for 90° metal-ligand-metal links, \({t}_{2g}^{5}\) transition ions, and sizable spin-orbit coupling. It is being studied in honeycomb compounds but also on triangular lattices. While for the former it is known by now that the Kitaev intersite couplings are ferromagnetic, for the latter the situation is unclear. Here we pin down the exchange mechanisms and determine the effective coupling constants in the \({t}_{2g}^{5}\) triangular-lattice material NaRuO₂, recently found to host a quantum spin liquid ground state. We show that, compared to honeycomb compounds, the characteristic triangular-lattice cation surroundings dramatically affect exchange paths and effective coupling parameters, changing the Kitaev interactions to antiferromagnetic. Quantum chemical analysis combined with subsequent effective spin model simulations provide perspective onto the nature of the experimentally observed quantum spin liquid—it seemingly implies fairly large antiferromagnetic second-neighbor isotropic exchange, and the atypical proximity to ferromagnetic order is related to ferromagnetic nearest-neighbor Heisenberg coupling.

Kitaev 交换是量子磁性研究的一种新范式，发生在 90° 金属-配体-金属连接、\({t}_{2g}^{5}\)过渡离子和相当大的自旋轨道耦合中。人们正在对蜂窝状化合物以及三角晶格进行研究。对于前者，目前已知基塔耶夫位点耦合是铁磁的，而对于后者，情况尚不清楚。在这里，我们确定了交换机制并确定了三角晶格材料 NaRuO _{2中的有效耦合常数}（{t}_{2g}^{5}\），最近发现存在量子自旋液态基态。我们表明，与蜂窝状化合物相比，特征性的三角晶格阳离子环境显着影响交换路径和有效耦合参数，将基塔耶夫相互作用改变为反铁磁性。量子化学分析与随后的有效自旋模型模拟相结合，为实验观察到的量子自旋液体的性质提供了视角——它似乎意味着相当大的反铁磁第二邻居各向同性交换，并且与铁磁有序的非典型接近与铁磁最近邻海森堡有关耦合。