The van der Waals bonded transition metal phosphorous trichalcogenides FePS₃, NiPS₃ and MnPS₃ have recently attracted renewed attention due to the possibility of exfoliating them into their monolayers. Although the three compounds have similar electronic structure, the magnetic structure differs due to subtle differences in exchange and magnetic anisotropy and the materials thus comprise a unique playground for studying different aspects of magnetism in 2D. Here we calculate the exchange and anisotropy parameters of the three materials from first principles paying special attention to the choice of Hubbard parameter U. We find a strong dependence of the choice of U and show that the calculated Nel temperature of FePS₃ varies by an order of magnitude over commonly applied values of U for the Fe d-orbitals. The results are compared with parameters fitted to experimental spin-wave spectra of the bulk materials and we find excellent agreement between the exchange constants when a proper value of U is chosen. However, the anisotropy parameters are severely underestimated by density functional theory and we discuss possible origins of this discrepancy.

范德华键合的过渡金属磷三硫属化物 FePS ₃、NiPS ₃和 MnPS ₃最近由于有可能将它们剥离成单层而引起了新的关注。尽管这三种化合物具有相似的电子结构，但由于交换和磁各向异性的细微差异，磁性结构有所不同，因此这些材料构成了研究二维磁性不同方面的独特场所。这里我们从第一性原理计算三种材料的交换和各向异性参数，特别注意哈伯德参数U的选择。我们发现U的选择有很强的依赖性并表明计算出的 FePS _{3 的}Nel 温度比通常应用的 Fe d轨道的U值变化一个数量级。将结果与安装在散装材料的实验间旋转波谱的参数进行比较，并且在选择U的适当值时，我们在交换常数之间找到了很好的一致性。然而，密度泛函理论严重低估了各向异性参数，我们讨论了这种差异的可能起源。