Cluster Self-Organization of Intermetallic Systems: New Cluster-Precursors K12 = 1Zn@11(Mg5Zn6), K5 = 0@5(LiZn4), K4 = 0@4(Li2Al2) in the Li12Mg20Al8Zn60-oC100 Crystal Structure and K3 = 0@3(CaMgGe), K4 = 0@4(LiCaMgGe), K4 = 0@4(Ca2Ge2) in the Li4Ca32Mg8Ge32-oP76 Crystal Structure
V. Ya. Shevchenkoa, * and G. D. Ilyushinb,**
a Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, 199034 Russia
b Federal Research Center “Crystallography and Photonics,” Moscow, 119333 Russia
Correspondence to: *e-mail: shevchenko@isc.nw.ru
Correspondence to: **e-mail: ilyushin@mail.ru
Received 6 September, 2022
Abstract—Geometrical and topological analysis of the crystal structures Li12Mg20Al8Zn60-oC100 (a = 5.102 Å, b = 23.477 Å, c = 13.691 Å, V = 1639.90 Å3, space group Cmcm) and Li4Ca32Mg8Ge32-oP76 (a = 21.98 Å, c = 18.560 Å, V = 1826.58 Å3, space group Pnma) are performed using computer methods (ToposPro software package). For the Li12Mg20Al8Zn60-oC100 three cluster precursors K12, K5, and K4 have been established. The cluster K12 = 1Zn@11(Mg5Zn6) in the form of coupled planar 5th rings Mg5 and Zn5, with Zn atoms located above their centers with symmetry m2m. The cluster K5 = 0@5(LiZn4) is in the form of a triangular bipyramid LiZn4 with symmetry 2. The cluster K4 = 0@4(Li2Al2) is in the form of a tetrahedra Li2Al2 with symmetry 2. For the Li4Ca32Mg8Ge32-oP76 two topological types of clusters have been established: triple ring K3 = 0@3(CaMgGe), tetrahedra K4 = 0@4(LiCaMgGe), and tetrahedra K4 = 0@4(Ca2Ge2). Clusters K3 = 0@3(CaMgGe) and K4 = 0@4(LiCaMgGe) form a suprapolyhedral ensemble (the tetramer) of four linked clusters 2(K3 + K4) with symmetry –1 centered at position 4a. Tetrahedra K4 = 0@ 4(Ca2Ge2) form a suprapolyhedral ensemble (the hexamer) of 6 linked clusters with symmetry –1. The symmetry and topological code of the processes of self-assembly of crystal structures Li12Mg20Al8Zn60-oC100 and Li4Ca32Mg8Ge32-oP76 from cluster precursors has been reconstructed in the form: primary chain → layer → framework.
Keywords: Li12Mg20Al8Zn60-oC100, Li4Ca32Mg8Ge32-oP76, self-assembly of crystal structure, precursor clusters K12, K5, K4, K3
DOI: 10.1134/S1087659622600612