Exploring High-Pressure Lithium Beryllium Hydrides: A New Chemical Perspective

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• 作者：Yuanzheng Chen ; Feng Peng ; Yan Yan ; Ziwei Wang ; Chenglin Sun ; Yanming Ma
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：July 11, 2013
• 年：2013
• 卷：117
• 期：27
• 页码：13879-13886
• 全文大小：584K
• 年卷期：v.117,no.27(July 11, 2013)
• ISSN：1932-7455

文摘

Lithium beryllium hydrides are known as high gravimetric hydrogen density (GHD) hydrogen-storage materials. However, the lithium beryllium hydrides that can be experimentally synthesized remain scarce. Here we report a computer design on novel hydrides of LiBe₂H₅ and LiBeH₅ with higher GHD synthesizable at high pressures by using a first-principles CALYPSO technique on crystal structure prediction. It was found that LiBe₂H₅ and LiBeH₅ become thermodynamically stable above 228 and 67 GPa, respectively, with respect to various decomposition routes. In their stable states, LiBe₂H₅ adopts a layered ionic I4/mcm structure, characterized by Li⁺ cations together with negatively charged polymeric networks consisting of BeH₈, while LiBeH₅ takes hydrogen sublattices composed of either H₂ molecules or H₃^{鈥?/sup> structural units. The nature and the strength of covalent and ionic bonding of these stable states were identified and analyzed to compare with the high pressure structures of BeH₂. In contrast with the stubborn insulating character of the Li_nBe_mH_n+2m systems (n and m are integers, e.g., LiBeH₃, Li₂BeH₄, and LiBe₂H₅), the metallization of LiBeH₅ and BeH₂ takes place at high pressures and their structures experience either a strengthening of covalency in LiBeH₅ within the H₃鈥?/sup> units or a weakening of ionic character in BeH₂ due to the missing of low-electronegativity lithium atom. Our findings quest future experiments to synthesize these high GHD hydrogen-storage materials.}