Prediction of LinCd Compounds With Unusual Stoichiometry and Valence States

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Physical Review Materials





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Cadmium (Cd) and its compounds are a family of materials exhibiting diverse physical and chemical properties that find wide-ranging applications in many science and technology fields. In all known Cd compounds, Cd ions behave like a typical d-block element, donating electrons and adopting positive (+2 or +1) charge states. To explore the possibility of forming compounds with Cd in negative charge states, would greatly expand this material family and enrich understanding of the associated physical and chemical properties and the underlying mechanisms. Here, we report on an exemplary case study via a systematic search and examination of Li-Cd binary compounds over a wide range of stoichiometry. We have employed an unbiased crystal structure search method in conjunction with first-principles energetic calculations to predict viable crystal structures under ambient and high-pressure conditions. Our investigations have identified a series of stable LinCd compounds with an unusually wide range (n = 1–6) of stoichiometry at both ambient and high pressures. Strikingly, our results reveal that Cd attracts electrons from Li in forming a rich variety of bonding configurations with the Cd ions adopting a range of negative charge states, producing highly tunable structural and electronic properties. Moreover, calculated elastic parameters show that the mechanical properties of LiCd compound can be enhanced considerably over those of Li and Cd metals and other Li-Cd binary compounds. We analyze the charge transfer from Li to Cd and the resulting electron distribution patterns and find a significant and variable amount of partial occupation of the Cd-5p states in this traditional d-block element. The present findings provide insights into fundamental knowledge and practical processes in valence state control for tuning transitions from d- to p-block behaviors via a proper choice of compound formation and application of high pressure. The results expand conventional definition and understanding of charge states in the compound formation and enrich structure-property relations that have broad implications for Li-rich binary compounds.


Physical Chemistry



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