四方Mo_2B基本物性的第一性原理研究  

First-principle Study on Basic Physical Properties of Tetragonal Mo_2B

作　　者：蒋华龙[1] 濮春英[1] 杨兴强[1] 宋海珍[1] 张飞武[2,3] 周大伟[1] 

机构地区：[1]南阳师范学院物理与电子工程学院,南阳473061 [2]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵阳550002 [3]科廷大学纳米化学研究所

出　　处：《人工晶体学报》2015年第7期1983-1989,1996,共8页Journal of Synthetic Crystals

基　　金：国家自然科学基金(11247222;U1304612;U1404608);河南省教育厅高等学校重点科研项目(15B140006)

摘　　要：采用基于密度泛函理论的第一性原理方法，对新近发现的四方M02B在0-40GPa压力范围内的物性进行了研究，研究内容包括弹性、各向异性、脆性延展性、硬度、理论强度、热容、热膨胀系数等基本物理性质。研究发现在0-40GPa压力范围内，四方Mo2B晶体均满足力学稳定性条件，并且表现出较强的各向同性。同时发现该晶体具有较高的抗压缩能力，但抗剪切能力较差，抗压和抗剪切能力会随压力增加而增长。此外还发现四方Mo2B为韧性材料，且压力越大韧性越强。计算显示它的维氏硬度为14．3GPa，限制其作为超硬材料的应用。通过应力一应变的计算发现其不同方向的理想拉伸及剪切强度都比较低。此外，还利用准谐德拜模型研究了四方Mo2B的热膨胀系数以及定容热容等热力学性质。Using first-principles calculations based on density-functional theory, the basic physical properties of thenewly found tetragonal Mo2B at 0-40 GPa including elasticity, elastic anisotropy, brittleness or ductility, hardness, ideal strength, heat capacity, thermal expansion coefficient were investigated. It is found that the tetragonal Mo2B is mechanically stable and shows a strong isotropic behavior in the pressure range from 0 to 40 GPa. Moreover, the crystal has high compression resistance, but poor ability to resist shear. Both the bulk and shear modulus increase with increasing pressure. It is also found that tetragonal Mo2B is a ductile material, and the higher the applied pressure, the greater the ductility. The Vickers hardness of the tetragonal MOEB is calculated to be about 14.3 GPa, which limits its use as a potential superhard material. The stress-strain curve calculation reveals that the ideal tensile and shear strengths are very low though. In addition, the thermal expansion coefficient and heat capacity at constant volume were investigated using the quasi-harmonic Debye model.

关 键 词：第一性原理 弹性性质 热力学性质 Mo2B 

分 类 号：O469[理学—凝聚态物理]