掺杂BaHfO_3电子结构与力学性能的第一性原理研究

First-principles study of electronic structure and mechanical characteristics of doping BaHfO_3

在广义梯度近似(GGA)下,采用基于密度泛函理论的第一性原理方法研究了掺杂对BaHfO3的电子结构与力学性能的影响.电子结构计算表明:优化的BaHfO3晶格常数与实验值吻合较好,BaHfO3为一种间接带隙的绝缘体材料.掺杂Sr和Ti后该材料仍为间接带隙材料,Ba0.5Sr0.5HfO3的带隙增大,绝缘体特征增强,而BaHf0.5Ti0.5O3的带隙显著减小,呈现出半导体材料的特征.由态密度分析可知,掺杂后带隙的变化主要是由于导带底的移动造成的.力学性能分析表明:与BaHfO3相比,Ba0.5Sr0.5HfO3的剪切模量和杨氏模量均明显减小,材料硬度减弱;BaHf0.5Ti0.5O3的剪切模量及杨氏模量均明显增大,材料硬度增强.电子密度分布分析揭示了掺杂改变体系价电子浓度的分布情况,使BaHfO3的价健特性发生了变化,这是材料硬度改变的内在原因.可见,掺杂能够有效地调控体系的硬度,该研究结果为掺杂BaHfO3力电材料的设计与应用提供了理论依据.

The influences of doping on electronic structures and mechanical properties of BaHfO3 are in- vestigated by using first-principles plane-wave density functional theory within the generalized gradient approximation （GGA）. The electronic structure calculations show that the lattice constant of optimized BaHfO3 agrees with the experimental value, and BaHfO3 and doped BaHfO3 with Sr or Ti are both indi- rect band gap materials. Specifically, the band gap of Ba0.5 Sr0.5 HfO3 increases and the characteristics of insulator enhances, while the band gap of BaHf0.5Ti0.5O3 is obviously reduced and the features of semi-conductor material are displayed. The analysis of the density of states shows that the change of the band gap after doping is due mainly to the movement of the bottom of conduction band. The analysis of me- chanical properties indicates that the shear modulus and Young＇s modulus of Ba0.5 Sr0.5 HfO3 decrease comparing with BaHfO3, which leads to the decrease of the hardness of the material. But for BaHf0.5 Ti0.503, both the shear modulus and Young＇s modulus increase, which causes the enhance of hardness. Electron density distribution analysis reveals that the doping changes the valence electron concentration distribution of the system, resulting in the change of bonding characteristics of BaHfO3, and this is the underlying reason for the change of hardness of the material. Thus, the doping can effectively control the hardness of the system. The results of the study provide a theoretical basis for the design and appli- cation of doping BaHfO3 electromechanical materials.