在Fe1-xCoxSe2系列中对marcasite-pyrite多形体形成进行合成控制
Synthetic control over marcasite-pyrite polymorph formation in the Fe1-xCoxSe2 series
AI总结：
通过组合沉积与体外硒化方法，在低温下成功合成marcasite结构的CoSe2，并揭示其为Fe1-xCoxSe2系列的平衡相。
摘要：
过渡金属二硫化物的pyrite-marcasite家族是晶体化学的模型系统。其中一些材料表现出多形性。CoSe2的理论基态是marcasite，但该材料通常以pyrite结构合成。多形性已在纳米颗粒中被观测到，但尚未实现对CoSe2多形体的合成控制。我们通过结合组合沉积和体外硒化方法，合成了Fe1-xCoxSe2系列的材料库。该方法允许高效地探索不同合成条件下形成的替代范围和晶体结构。我们发现，在低温下合成时，marcasite结构中较高的Co含量是可能的。在仅250°C的合成温度下，我们成功合成了以marcasite CoSe2为主要相的材料。密度泛函理论模拟显示，CoSe2的两种同形体在能量上极为接近，且正交相是能量基态。我们的实验和理论数据表明，marcasite结构是Fe1-xCoxSe2在整个组成范围内的平衡相。
英文摘要：
Transition-metal dichalcogenides of the pyrite-marcasite family are model systems of crystal chemistry. A few of these show polymorphism. The theoretical ground state of CoSe2 is marcasite, but the material is typically synthesized in the pyrite structure. Polymorphism has been observed in nanoparticles and synthetic control of the polymorphs of CoSe2 has not been achieved. We have synthesized material libraries of the Fe1-xCoxSe2 series by combining combinatorial deposition and ex-situ selenization. The approach allows to efficiently explore substitution ranges and crystal structures that form for different synthesis conditions. We find that higher levels of Co content x within the marcasite structure are possible when synthesizing at low temperatures. At a synthesis temperature of only 250° C, we have successfully synthesized marcasite CoSe2 as the majority phase. Density functional theory simulations reveal that the two isomorphs of CoSe2 are extremely close in energy and that the orthorhombic phase is the energetic ground state. Our experimental and theoretical data show that the marcasite structure is the equilibrium phase of Fe1-xCoxSe2 in the entire composition range.
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