Crystal structures of M₂[B₁₀H₁₀] (M = Na, K, Rb) via real-space simulated annealing powder techniques

Abstract

Decahydro-closo-decaborates / Simulated annealing / Powder diffraction structure analysis / X-ray diffraction Abstract. Alkali metal decahydro-closo-decaborates M 2 [B 10 H 10 ] (M ¼ Na, K, Rb) were synthesised by ionexchange and characterised via infrared and 11 B-NMR spectroscopy. The crystal structures of Na 2 [B 10 H 10 ], K 2 [B 10 H 10 ], and Rb 2 [B 10 H 10 ] were determined from X-ray powder diffraction data using real-space techniques. The compounds crystallise in the monoclinic space group P2 1 /n (no. 14) with the lattice constants: Na 2 [B 10 H 10 ]: a ¼ 1028.28 (6) pm, b ¼ 1302.18(5) pm, c ¼ 667.34(3) pm, b ¼ 93.754(3) ; K 2 [B 10 H 10 ]: a ¼ 1285.54(8) pm, b ¼ 1117.84(7) pm, c ¼ 682.27(4) pm, b ¼ 93.357(3) ; Rb 2 [B 10 H 10 ]: a ¼ 1320.04(7) pm, b ¼ 1136.88(6) pm, c ¼ 704.23(4) pm, b ¼ 94.158(3) . The hydroborate anions are arranged almost hexagonally with alkali metal cations in the tetrahedral interstices.

Comparison of Anion Reorientational Dynamics in MCB9H10 and M2B10H10 (M = Li, Na) via Nuclear Magnetic Resonance and Quasielastic Neutron Scattering Studies

“…This value is close to the observed main "step" of Δ H from 58 to 17 kHz (∼70% drop) in Na 2 B 10 H 10 ( Figure 5). We are currently attempting to verify the presence of such distinct types of reorientational jumps and their relative frequencies with QENS in an analogous heavier-metal analogue such as Rb 2 B 10 H 10 , which also possesses an ordered monoclinic structure, 37 but unlike Na 2 B 10 H 10 , one that persists up to much higher temperatures.…”

The low-temperature structural behavior of sodium 1-carba-closo-decaborate: NaCB9H10

“…Although the structural details for the disordered phases of these two compounds are known [6], no definitive information has been reported, as of yet, concerning their lowtemperature ordered structures. The related Li 2 B 10 H 10 and Na 2 B 10 H 10 compounds with geometrically similar but divalently charged decahydro-closo-decaborate B 10 H 10 2anions are known to display ordered structures with respective hexagonal [8] and monoclinic symmetries [9,10]. Yet, one cannot assume that these same structural symmetries will apply to the ordered LiCB 9 H 10 and NaCB 9 H 10 phases, since one must take into account the structural consequences of the marked differences in anion valencies and charge polarizations between [5].…”

Inorganic Solid Electrolytes for All‐Solid‐State Sodium Batteries: Fundamentals and Strategies for Battery Optimization

“…[ 78 ] According to the paddlewheel mechanism, the rotating anions aid cation diffusional jumps and flatten the energy landscape. [ 18a,28d,39,79 ] Therefore, the ionic conductivity of the HT phases is obviously superior to those of low‐temperature phases (Figure 14b).…”