Electron-rich rods as building blocks for Sb strips and Te sheets.

Abstract

We analyze the bonding in a number of networks of heavy main group elements comprised of finite-length linear chains fused at right angles. Isolated linear chain building blocks may be understood easily by analogy with three-orbital four-electron "hypervalent" bonding picture in such molecules as I(3)(-) and XeF(2). After deriving the appropriate electron-counting rules for such linear units, we proceed in an aufbau to fuse these chains into simple (and not so simple) infinite networks. It is proposed that (a) infinite Sb(3) ribbons of vertex sharing squares are stable for an electron count of 20 electrons per three atoms (i.e., ); (b) sidewise fused Sb double ribbons are stable for an electron count of 38 electrons per six atoms (i.e., ); (c) Sb(4) strips cut from a square lattice are stable at the electron count of 24 electrons per four atoms (i.e., ); (d) Te(6) defect square sheets are stable at the electron count of 40 electrons per six atoms (i.e., ). The electronic structures of the solid-state compounds containing these networks, namely La(12)Mn(2)Sb(30), alpha-ZrSb(2), beta-ZrSb(2), Cs(3)Te(22), and Cs(4)Te(28), are elaborated. We propose preferred electron counts for two hypothetical Sb ribbons derived from the Sb(3) ribbon in La(12)Mn(2)Sb(30). A possibility of geometry distortion modulation by excess charge in lattices comprised of even-membered linear units is suggested.