A Systematic Study of Structures, Stability, and Electronic Properties of alloy clusters AlBen (n = 1–12): Comparison with Pure Beryllium Clusters
Dan Yu, 11Institute of Theoretical Chemistry, Jilin University, Changchun 130023, (P. R. China)Wei-Ming Sun, 22The School of Pharmacy, Fujian Medical University, Fuzhou 350108, (P. R. China) Jing-Yao Liu,1 Di Wu,1 Ying Li,1 and Zhi-Ru Li1
Correspondence to: Wei-Ming Sun (E-mail:sunwm@fjmu.edu.cn); Ying Li (E-mail: liyingedu@jlu.edu.cn )
Introduction
As a bridge between atoms and macroscopic state, cluster science continues to be a subject of increasing research interest. In the realm of cluster investigations, metal clusters[1–7]have attracted extensive attention in the last several decades because they exhibit many intriguing properties that are neither atomic-like nor extended solidlike,[8,9] while being closely connected to size, geometry, and composition. These size-dependent properties offer exciting possibilities for developing finely tuned cluster-assembled materials, which have promising applications in the fields of material science, optics, nanotechnology, catalysis, etc.[10–14]Besides, it has long been recognized that the properties of metal clusters, instead of evolving linearly with size, usually vary discontinuously with the number of component atoms.[11] In this respect, a simple yet helpful free-electron model, namely spherical jellium model (SJM),[15] has been proposed to account for the evolution of properties (even structures) of numerous pure and doped metal clusters.[16,17]
The fact that beryllium dimer is weakly bound[18–22] whereas bulk beryllium is a hard metal with rather high melting point and enthalpy of atomization[23] makes beryllium cluster an ideal prototype for exploring the evolution from discrete molecules to metallic state, as indicated in an overview on the studies of beryllium clusters.[24] In contrast to experimental studies which are limited by the toxicity of beryllium, quantum chemistry provides powerful computational methods that help to investigate beryllium clusters in detail. By using density functional theory with Becke–Lee–Yang–Parr gradient correction, Wang et al.[25] studied the structural and electronic properties of beryllium clusters containing up to 21 atoms, and they found that the Be4, Be10 and Be17 clusters show particularly high stability. With the help of a modified genetic algorithm, Khanna and coworkers[26] have revealed the dependence of relative stability and electronic properties of the Ben (n = 2 − 41) clusters on their equilibrium geometries.
Recently, doped metal clusters have attracted much attention from both theoretical and experimental researchers. It has been found that the characteristics of pure metal clusters, such as relative stability, structural evolution, bonding character, electronic and magnetic properties, etc., are usually altered when a heteroatom is introduced. Consequently, doped clusters may show new physicochemical properties not found in pure clusters. In this study, we focus on doped beryllium clusters and choose Al atom as the dopant atom. On the one hand, impurity-atom doping may provide additional flexibility to modulate the physical and chemical properties of beryllium clusters. On the other hand, the systematical study of beryllium-aluminum binary clusters is a meaningful project in view of the important applications of Be-Al alloys in disk drive armatures, automotive braking systems, and aerospace and satellite system components.[27-30]
In the present work, we have performed a comprehensive study of the bimetallic AlBen (n = 1–12) clusters. Besides exploring the ground state structures, we also aim to reveal the evolution of structures, stability, and various electronic structure related properties of AlBen along with cluster size. Furthermore, we make a comparison between AlBen and pure Ben +1clusters from all aspects to analyze the Al-substitution effect. We hope that results from this study will not only offer a fundamental understanding of structure-property relationship of subnano-scale beryllium-aluminum clusters, but provide useful references for studies of other binary metal clusters.