NiAl中Ni空位对杂质C原子的多重俘获及温度效应的第一性原理研究  

First-principles studies of multiple trapped impurity C by Ni vacancy and temperature effects in NiAl intermetallics

作　　者：胡雪兰[1] 罗阳[1] 赵若汐 胡艳敏[1] 张艳峰[1] 宋庆功[2] 

机构地区：[1]中国民航大学中欧航空工程师学院,天津300300 [2]中国民航大学理学院,天津300300

出　　处：《物理学报》2016年第20期178-184,共7页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:51201181);中国民航大学科研启动基金(批准号:08QD14X)资助的课题~~

摘　　要：本文应用基于密度泛函理论的第一原理方法,研究了NiAl金属间化合物中Ni空位对杂质C元素的多重俘获.研究结果表明:在Ni空位存在时,单个C原子最易于存在于空位中心附近的富Ni八面体间隙位置且与邻近的Ni原子和Al原子之间存在共价键形式的相互作用.多个C原子在NiAl中倾向于以"Sequential"的方式被Ni空位俘获,进而形成CnVNi(n=1,2,3,4)团簇.通过电荷密度和差分电荷密度分析得到,当Ni空位俘获多个C原子后,C原子之间有着优先于自身成键的特性.进一步,我们应用热力学模型计算了温度对于C_nV_(Ni)(n=1,2,3,4)团簇浓度及空位浓度的影响.研究表明本征Ni空位的浓度会随着温度的升高而升高.在NiAl金属间化合物中,大多数的杂质C原子会被Ni空位俘获而不是存在于远离Ni空位的八面体间隙位置.由于C原子被Ni空位俘获的过程是一个放热过程,使得体系温度升高,因此会进一步激发更多的Ni空位产生.但是在一定的温度范围内(温度小于700 K时),Ni空位均以C_nV_(Ni)团簇的形式存在.By using a first-principles pseudopotential method based on the density functional theory and Vienna ab initio Simulation Package（VASP）, we investigate the multiple trapping of C by Ni vacancy（VNi） and its temperature effects in NiAl intermetallics. A single C atom is energetically and favorably situated at the Ni-rich octahedron interstitial site that surrounds Ni vacancy, which is shown via calculating the formation energy of C atom in NiAl with Ni vacancy system. Single C atom prefers to interact with neighboring Ni atom and Al atom to form a covalent bond. In NiAl intermetallics, C atoms prefer to be trapped in the Ni vacancy in the ＂sequential＂ way, thus easily forming the CnVNi（n = 1, 2, 3, 4） clusters, in which the C4V（Ni） clusters are most energetically favorable. It is interesting to find that when C atoms are trapped by Ni vacancy, all the C atoms themselves prefer to be combined with each other to form a bond,surrounding Ni vacancy. With the C atoms further added, both the charge density and the deformation charge prefer to bind with each other despite the Ni or Al environment and the intrinsic bonding properties of C—C bond contain obvious covalent characteristics. Furthermore, using first-principles calculations combined with statistical model, we quantitatively predict point defect concentration as a function of temperature in NiAl intermetallics. It is concluded that the concentration of intrinsic Ni vacancies（VNi） will obviously increase as temperature increases. With the increase of temperature, the concentration of C atoms in the CnVNi cluster is higher than that at the intrinsic position. Besides,it indicates that most of C atoms in NiAl intermetallics are trapped by Ni vacancy, which is due to the larger binding energy of the CnVNi clusters and most of the C atoms are trapped directly by vacancies at room temperature or high temperature to form CnVNi clusters. Since the formation of CnVNi clusters is a process of heat releasing which will further increase the temperat

关 键 词：NIAL金属间化合物 杂质碳 多重俘获 温度效应 

分 类 号：O469[理学—凝聚态物理]