What is the correct low-energy spin Hamiltonian description of \(\alpha\)-RuCl\(_{3}\)? The material is a promising Kitaev spin liquid candidate, but is also known to order magnetically, the description of which necessitates additional interaction terms. The nature of these interactions, their magnitudes and even signs, remain an open question. In this work we systematically investigate dynamical and thermodynamic magnetic properties of proposed effective Hamiltonians. We calculate zero-temperature inelastic neutron scattering (INS) intensities using exact diagonalization, and magnetic specific heat using a thermal pure quantum states method. We find that no single current model satisfactorily explains all observed phenomena of \(\alpha\)-RuCl\(_{3}\). In particular, we find that Hamiltonians derived from first principles can capture the experimentally observed high-temperature peak in the magnetic specific heat, while overestimating the magnon energy at the zone center. In contrast, other models reproduce important features of the INS data, but do not adequately describe the magnetic specific heat. To address this discrepancy we propose a modified ab initio model that is consistent with both magnetic specific heat and low-energy features of INS data.

\（\ alpha \）- RuCl \（_ {3} \）的正确的低能自旋哈密顿量描述是什么？该材料是有前途的Kitaev自旋液体候选物，但也已知在磁性上有序，其描述需要其他相互作用项。这些相互作用的性质，程度甚至标志仍然是一个悬而未决的问题。在这项工作中，我们系统地研究了提出的有效哈密顿量的动力学和热力学磁性。我们使用精确的对角线化计算零温度非弹性中子散射（INS）强度，并使用热纯量子态方法计算磁比热。我们发现没有一个单一的电流模型可以令人满意地解释\（\ alpha \）- RuCl的所有观察到的现象\（_ {3} \）。特别是，我们发现从第一性原理推导出的哈密顿量可以捕获磁比热中实验观察到的高温峰，同时高估了区域中心的磁振子能量。相反，其他模型重现了INS数据的重要特征，但是没有充分描述磁比热。为了解决这一差异，我们提出了一种改进的从头算模型，该模型与磁性比热和INS数据的低能特征均一致。