Study of Crystal Structure, Electronic Structure and Magnetic Properties of CaMnO₃ from Hybrid Functional Approach

基于杂化密度泛函理论，我们研究了钙钛矿型过渡金属氧化物CaMnO3的晶格结构和电子结构，并与传统的局域密度近似和广义梯度近似相比较。计算表明杂化泛函给出的晶体结构与实验结果非常吻合，同时2.5 eV大小的能隙与实验上测得的3.1 eV也十分接近。更进一步，我们计算了Mn4+离子间的磁交换作用系数，并用蒙特卡罗方法估算出体系的尼尔温度为87 K，这与实验上的131 K也比较符合。这些结果表明杂化泛函可以很好预测绝缘型过渡金属氧化物的物理性质。 Based on the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional theory, we have studied the crystal structure, electron structure, and magnetic properties of perovskite transition metal oxide CaMnO3. Compared with traditional local density approximation and generalized gradient approximation, the crystal structure within HSE is in good agreement with experimental data. In addition, a 2.5 eV band gap is close to 3.1 eV from experiment. Furthermore, with the magnetic exchange coupling constants, the magnetic transition Neel temperature of CaMnO3is 87 K, consistent with the experiment value of 131 K. These findings indicate that the hybrid functional could provide a proper description of insulating transition metal oxides.