Lithiation-induced zinc clustering of Zn3, Zn12, and Zn18 units in Zintl-like Ca∼30Li3+xZn60-x (x = 0.44-1.38).
Zinc clusters are not common for binary intermetallics with relatively low zinc content, but this work shows that zinc clustering can be triggered by lithiation, as exemplified by Ca(∼30)Li(3+x)Zn(60-x), P6/mmm, Z = 1, which can be directly converted from CaZn(2). Two end members of the solid solution (x = 0.44 and 1.38) were established and structurally characterized by single-crystal X-ray diffraction analyses: Ca(30)Li(3.44(6))Zn(59.56(6)), a = 15.4651(9) Å, c = 9.3898(3) Å; Ca(30.45(2))Li(4.38(6))Zn(58.62(6)), a = 15.524(3) Å, c = 9.413(2) Å. The structures of Ca(∼30)Li(3+x)Zn(60-x) feature a condensed anionic network of Zn(3) triangles, lithium-centered Zn(12) icosahedra, and arachno-(Zn,Li)18 tubular clusters that are surrounded respectively by Ca(14), Ca(20), and Ca(30) polyhedra. These polyhedra share faces and form a clathrate-like cationic framework. The specific occupation of lithium in the structure is consistent with theoretical "coloring" analyses. Analysis by the linear muffin-tin orbital (LMTO) method within the atomic sphere approximation reveals that Ca(∼30)Li(3+x)Zn(60-x) is a metallic, Zintl-like phase with an open-shell electronic structure. The contribution of Ca-Zn polar covalent interactions is about 41%.
Division of Materials Science and Engineering, Ames Laboratory, U.S. Department of Energy , Ames, Iowa 50011 United States.
Qisheng
Q
Lin