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On the structure of heptalithium distannide: Li7Sn2 or Li7−xSn2 (0.3 < x < 0.5).

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Title: On the structure of heptalithium distannide: Li7Sn2 or Li7−xSn2 (0.3 < x < 0.5).
Authors: Rahman, Salina, Ghosh, Kowsik, Ovchinnikov, Alexander, Nandakumar, Anirudh, Chan, Candace K., Bobev, Svilen
Source: Dalton Transactions: An International Journal of Inorganic Chemistry; 9/14/2025, Vol. 54 Issue 34, p12859-12867, 9p
Subject Terms: CRYSTAL structure, X-ray diffraction, INTERMETALLIC compounds, ORDER-disorder transitions, CHEMICAL bonds, NONSTOICHIOMETRIC compounds
Abstract: Li–Sn intermetallics are promising candidates for high-capacity Li-ion battery anodes, yet, the precise crystal structures of some "known" binary phases remain unresolved. One such phase, Li7Sn2, originally reported in 1975, is re-examined here using single-crystal X-ray diffraction methods. Its orthorhombic structure (space group Cmmm, no. 65) features isolated Sn atoms and Sn–Sn dumbbells in a matrix of Li atoms. The present study indicates occupational disorder on one of the Li sites in Li7Sn2, meaning that it is a non-stoichiometric phase with revised composition of Li7−xSn2 (0.3 < x < 0.5). In the most extreme case, when the Li atomic site in question is completely empty, the composition becomes Li6.5Sn2 or Li13Sn4. Analysis of the chemical bonding through electronic structure calculations indicates significant covalency of Sn–Sn and Li–Sn interactions. [ABSTRACT FROM AUTHOR]
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Database: Complementary Index
Description
Abstract:Li–Sn intermetallics are promising candidates for high-capacity Li-ion battery anodes, yet, the precise crystal structures of some "known" binary phases remain unresolved. One such phase, Li<subscript>7</subscript>Sn<subscript>2</subscript>, originally reported in 1975, is re-examined here using single-crystal X-ray diffraction methods. Its orthorhombic structure (space group Cmmm, no. 65) features isolated Sn atoms and Sn–Sn dumbbells in a matrix of Li atoms. The present study indicates occupational disorder on one of the Li sites in Li<subscript>7</subscript>Sn<subscript>2</subscript>, meaning that it is a non-stoichiometric phase with revised composition of Li<subscript>7−x</subscript>Sn<subscript>2</subscript> (0.3 < x < 0.5). In the most extreme case, when the Li atomic site in question is completely empty, the composition becomes Li<subscript>6.5</subscript>Sn<subscript>2</subscript> or Li<subscript>13</subscript>Sn<subscript>4</subscript>. Analysis of the chemical bonding through electronic structure calculations indicates significant covalency of Sn–Sn and Li–Sn interactions. [ABSTRACT FROM AUTHOR]
ISSN:14779226
DOI:10.1039/d5dt01022e