钴基非晶态合金结构和性质的第一性原理模拟计算

发布时间：2018-07-22 21:35

【摘要】：本论文通过计算机模拟方法对钴基非晶态合金进行了研究,主要工作包括两部分。第一部分工作是采用从头计算分子动力学(ab initio molecular dynamics)模拟的方法研究了钴基非晶态合金(Co80P14B6,Co80P13C7和Co80B14C6)的原子结构,从而调查了类金属元素对钴基非晶态合金玻璃化形成能力和磁性能的影响。我们通过双体分布函数,Voronoi多面体和键对分析调查了这三个钴基非晶态合金在液态(1600 K)和玻璃态(300 K)下的局域原子结构。双体分布函数和Voronoi多面体分析指出,这三个钴基非晶态合金的玻璃化形成能力按Co80B14C6,Co80P13C7和Co80P14B6的顺序依次增加。同时,发现在三个钴基非晶态合金中,P原子有着和Co原子类似的局域结构,即P原子处在Co原子的替换位置。且以Co和P为中心的团簇较大,主要为类二十面体团簇。键对分析技术发现,这三个钴基非晶态合金的主要组成键对都是完美的或者扭曲的二十面体键对,如1551,1541和1431键对。基于态密度函数(density of state,DOS),我们计算了Co原子和类金属原子对于这三个非晶态合金平均磁矩的贡献。DOS分析发现,三个非晶态合金都显现出弱铁磁性,而且主要磁矩贡献均来自于Co的3d电子,而类金属原子在这三个非晶态合金中都呈现出相似的平均磁矩。第二部分工作可以细化为两个小部分:(1)研究类金属元素B的含量对钴基非晶态合金(CoTaB和CoNbB)的局域结构以及机械性能的影响。模拟计算结果显示,B原子的加入使得合金中0 3 6 0团簇的数目明显增加,同时也使得Co-B和B-B之间的共价键数目增多,而这种强共价键特性可能导致了合金的高强度。(2)探讨过渡族元素M(M=Ta,Nb和Mo)对CoMB非晶态合金的性能及强度的影响。结果显示,Ta和Nb的加入使得钴原子第一壳层原子配位几率增加,同时也使得CoTaB和CoNbB非晶态合金的短程有序性强于CoMoB非晶态合金。其次,我们发现三个Co基非晶态合金在中程序方面存在一定的有序性,而这种中程有序性跟普遍存在于这三个合金中的0 3 6 0团簇有着紧密的关系,很可能对于合金的强度有一定的贡献。
[Abstract]:In this paper, the cobalt-based amorphous alloy is studied by computer simulation. The main work consists of two parts. In the first part, the atomic structures of cobalt-based amorphous alloys (Co80P14B6, Co80P13C7 and Co80B14C6) were studied by ab initio molecular dynamics (ab initio molecular dynamics) simulation. The effect of metal-like elements on the glass forming ability and magnetic properties of cobalt-based amorphous alloys was investigated. The local atomic structures of the three cobalt-based amorphous alloys in liquid state (1600 K) and glass state (300K) have been investigated by means of double body distribution function Voronoi polyhedron and bond pair analysis. The distribution function and Voronoi polyhedron analysis show that the glass forming ability of the three cobalt-based amorphous alloys increases in the order of Co80B14C6 Co80P13C7 and Co80P14B6. At the same time, it is found that the P atom has a local structure similar to that of the Co atom in the three cobalt-based amorphous alloys, that is, the P atom is in the substitution position of the Co atom. The clusters centered on Co and P are larger, mainly icosahedron clusters. It is found that the three cobalt-based amorphous alloys are composed of perfect or twisted icosahedron bond pairs, such as 1551, 1541 and 1431 bond pairs. Based on the density of states function (density of), we calculated the contribution of Co atoms and metal-like atoms to the mean magnetic moments of the three amorphous alloys. The main contribution of magnetic moment comes from the 3D electrons of Co, and the metal-like atoms show a similar average magnetic moment in the three amorphous alloys. The second part can be divided into two parts: (1) the effect of the content of metal-like element B on the local structure and mechanical properties of cobalt-based amorphous alloys (CoTaB and CoNbB) is studied. The simulation results show that the addition of B atoms increases the number of 0.360 clusters and covalent bonds between Co-B and B-B. This strong covalent bond may lead to the high strength of the alloy. (2) the effect of transition group elements M (Mtadao Nb and Mo) on the properties and strength of CoMB amorphous alloy is discussed. The results show that the addition of Ta and NB increases the coordination probability of the first shell of cobalt atoms, and the short range ordering of CoTaB and CoNbB amorphous alloys is stronger than that of CoMoB amorphous alloys. Secondly, we find that there is a certain degree of order in the middle process of the three Co based amorphous alloys, and this intermediate range order is closely related to the 0.360 clusters that are ubiquitous in these three alloys. It is likely to contribute to the strength of the alloy.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.16

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