Cluster Self-Organization of Intermetallic Systems: New 143-Atom Icosahedral Nanocluster-Precursor and the Self-Assembly of a Crystalline Framework (Ba,Ca)46Li102 (R\(\bar {3}\)c, hR888)

Abstract

A combinational-topological analysis of the crystalline structure (Ba,Ca)₄₆Li₁₀₂ (R\(\bar {3}\)c, hR888, V = 30 978 ų) are performed by computers (the TOPOS software package). The framework-forming the 143-atom icosahedral nanocluster ico-K143 with a diameter of 20 Å is established by the method of the complete decomposition of a 3D atomic lattice into cluster structures. ico-K143 nanoclusters of a symmetry of g = \(\bar {3}\) are shown to be three-layered: Li @12(Li₁₂) @32(Li₁₂Ba₂₀) @98(Ba₃₂Li₆₆). The second shell corresponds to the Bergman cluster with 32, 90, and 60 peaks, edges, and faces, respectively. The third new type of icosahedral shell consisting of 98 atoms is characterized by 98, 288, and 192 peaks, edges, and faces, respectively. The chemical composition of the third shell is made up of Ba₃₂Li₆₆. In the third shell, 32 Ba atoms were located above all the 32 atoms of the Li₁₂Ba₂₀ shell. The symmetry and topological code of the self-assembly of 3D structures from iсo-K143 nanoclusters-precursors are simulated in the following form: primary chain → layer → framework. The iсo-K143 nanoclusters formed densely packed 2D layers 3⁶ positioned with a shift along the c axis. The distance between centers of iсo-K143 clusters is determined by the translation vector value a_hex = 19.913 Å. The large voids in the 3D framework are occupied by 12-atom Ba₃Li₉ clusters with the symmetry g = 32.