Application of BHMC Algorithm in the Stable Structure Optimation of Alloy Clusters

金属团簇由于其特殊性质，广泛地应用于物理、化学等众多领域。合金团簇充分地利用多种金属之间的协同效应实现了材料的多功能特性，而其稳定结构则是研究这些多功能特性的重要基础，因此备受关注。利用势能函数求解合金团簇稳定结构优化时，随着合金原子数的增加，合金团簇体系势能面上的局部极小值个数将会呈现指数倍数的增长，使得寻找高效的结构优化算法变得至关重要。传统的求解方法由于其求解的效率，难以获得较好质量的解，所以基于进化算法的团簇结构全局优化算法应运而生。 本文采用多体势Gupta势能函数来描述合金团簇原子之间的相互作用，以Fe-Pt二合金团簇为研究对象，结合合金团簇优化的不确定性，针对性地提出了基于改...Metallic clusters have great potentials in many fields such as physics and chemistry due to their unique property. Especially, the alloy clusters have received extensive attention because they can achieve bi-functional properties by the cooperative effect of different metals. For alloy clusters, the stable structure is extremely important for their multi-functional characteristics and applications...学位：工程硕士院系专业：航空航天学院_工程硕士(控制工程)学号：2322014115335

Structural optimization of Fe-n-Pt-m ( 5 <= n + m <= 24) alloy clusters based on an improved Basin-Hopping Monte Carlo algorithm

合金纳米团簇可以充分利用多种金属的协同效应来实现材料的多功能特性,因而备受关注.本文利用改进的Basin-Hopping Monte; Carlo算法研究了不同尺寸和不同比例下的Fe-Pt二元合金团簇的结构稳定性.为证明初始结构相关性,引入了相似函数来分析合金团簇稳定结构与其对应; 的单金属团簇结构之间的相似性,并分析了Fe-Pt合金团簇在稳定结构下的元素分布.研究结果表明:对于N ≤; 24的Fe-Pt合金团簇,其结构并没有随原子数的增长呈现出明显的形状变化.但是就原子分布而言,对于相同尺寸下不同比例的原子结构,Fe元素趋向于分; 布在外层,而Pt元素更趋向于分布在内层;对于相同比例不同尺寸的原子结构也得到了同样的结论,并且在Fe原子比例越大的情况下,这种趋向的分布越明显.; 此外,通过计算合金团簇与单一金属团簇的结构相似函数,发现N≤; 24的Fe-Pt合金团簇在吸收Fe单金属和Pt单金属基态结构的基础上,随着元素比例的变化,发生了不同于单金属基态结构的变化,并且不同比例结构差异; 较大.最后,通过计算Fe-Pt合金团簇能量的二阶有限差分值,在Fe-Pt表现出分离结构状态时找到了相对稳定度最好的稳定结构.Alloy nanoclusters have received extensive attention because they can achieve bifunctional properties by making good use of the cooperative effect of two metals. In this paper, an improved Basin-Hopping Monte Carlo (BHMC) algorithm is proposed to investigate the structural stabilities of Fe-Pt alloy nanoclusters. Different cluster sizes and chemical compositions are considered. Moreover, a similarity function is introduced to analyze the structural similarity between the stable structures of alloy clusters and those of their monometallic clusters. Meanwhile, the atomic distributions of Fe-Pt alloy clusters are considered for their stable structures. The results indicate that for Fe-Pt alloy clusters with the size N <= 24, there is no significant structural evolution with the increase of cluster size. Fe atoms prefer to segregate at the peripheral positions of the clusters, while Pt atoms tend to occupy the interior. The same distribution result can be obtained for the structures of clusters with different compositions. With Fe composition increasing, this distribution trend is more pronounced for the Fe-Pt alloy clusters.; In addition, by calculating the structural similarity function between alloy and monometallic clusters, we find that the stable structures of Fe-Pt alloy clusters gradually vary with composition ratio. Moreover, when the Fe atoms or Pt atoms are added into the Fe-Pt alloy system, they change the stable structures of Fe-Pt alloy clusters, resulting in a different structure from Fe and Pt monometallic ones. Also, the structural similarity is different when the Fe composition varies. Furthermore, the best stable structures of Fe-Pt clusters with different compositions and sizes are obtained by calculating the second-order finite difference in energy of Fe-Pt alloy clusters.National Natural Science Foundation of China [11474234, 51271156,; 61403318]; Fundamental Research Fund for the Central Universities, China; [20720160085