5d过渡金属二硼化物的结构和热、力学性质的第一性原理计算

利用基于密度泛函理论的第一性原理系统地研究了5d过渡金属二硼化物TMB₂ (TM=Hf–Au) 的结构、热学、力学和电学性质. 我们考虑了三种结构, 分别为AlB₂, ReB₂和WB₂结构. 计算得到的晶格常数与先前的理论和实验研究符合得很好. 通过计算生成焓预测了化合物的热力学稳定性; 从HfB₂到AuB₂, 生成焓的整体趋势是逐渐增加的. 在所考虑的结构中, 对HfB₂和TaB₂, AlB₂结构是最稳定的; 对WB₂, ReB₂, OsB₂, IrB₂和AuB₂, ReB₂结构是最稳定的; 对PtB₂, WB₂结构是最稳定的. 在所考虑的化合物中, ReB₂结构的ReB₂具有最大的剪切模量(295 GPa), 是最硬的化合物, 与先前的理论和实验结果相符. 计算得到的总态密度显示所有结构都具有金属特性. 讨论了系列化合物的变化趋势.关键词：弹性性质热力学性质第一性原理5d过渡金属二硼化物

First-principles calculations of structural thermodynamic and mechanical properties of 5d transitional metal diborides

The structural, thermodynamic, mechanical and electronic properties of 5d transitional metal diborides TMB₂ (TM=Hf-Au) are systematically investigated by first-principles within density functional theory. For each diboride, three structures are considered, i.e., AlB₂, ReB₂ and WB₂ structure. The calculated lattice parameters are in good agreement with previous theoretical and experimental results. From the calculated formation enthalpy, thermodynamic stability of compounds is predicted and the formation enthalpy increases from HfB₂ to AuB₂. Among the considered structures, AlB₂ structure is the most stable for HfB₂ and TaB₂; ReB₂ structure is the most stable for WB₂, ReB₂, OsB₂, IrB₂ and AuB₂; WB₂ structure is the most stable for PtB₂. The ReB₂ in ReB₂ structure has the largest shear modulus (295 GPa), and is the hardest compound, which is in agreement with previous theoretical and experimental results. The calculated density of states shows that they are all metallic. Their variation trends are discussed.