Superconductor ?
Superconductor ?
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超导体？
DOI：
10.4324/9780203732779-8
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发表时间：
2020
期刊：
影响因子：
9.8
通讯作者：
R. Ruoff
中科院分区：
文献类型：
--
作者：
R. Ruoff
评估了离子固体（NH 4）3C 60的生成焓（Δ Hf）。发现该固体相对于标准状态反应物（N2（g）、H2（g）和C60（s））是稳定的，其中Hf为-1.82eV/mol。为了比较，该生成焓小于例如，K3C60（-6.27 eV/mol）。（NH 4）3C 60作为一种新型的离子固体和潜在的超导体，如果能够合成的话，它将具有许多吸引人的特点。众所周知，NH 4阳离子的大小与Rb+的大小几乎完全相同。在M3 C60超导体中，Rb 3C 60具有第二高的超导转变温度，其Tc为28 K，这表明（NH 4）3C 60的Tc可能高于C60超导体，其中Cs3 C60（s）的Tc最高，为40 K。当NH 4抗衡阳离子被ND 4取代时，存在28%的相对质量变化，这比用碱金属原子可以实现的相对变化大得多，这对于研究同位素取代对Tc的影响是重要的。还有一种可能性是铵离子在晶格中旋转的独特动力学;如果固体是超导的，那么分子离子而不是原子离子的存在可能在超导机制中发挥作用。最后，与基于经由在密封管中升华的M的气相传输的M3 C60（M）的生产方法相比，将需要生产这种C60的铵盐的替代方法，例如电合成或在液氨中直接合成。
The enthalpy of formation ( ∆Hf) of the ionic solid (NH4)3C60 is assessed. The solid is found to be stable with respect to the standard state reactants (N 2(g), H2(g), and C60(s)), with a∆Hf of -1.82 eV/mol. For comparison, this enthalpy of formation is less than the enthalpy of formation of, e.g., K 3C60 (-6.27 eV/mol). There are several attractive features of (NH 4)3C60 as a new ionic solid and potential superconductor, if it can be synthesized . It is well-known that the size of the NH 4 cation is almost exactly the same as that of Rb+. Among the M3C60 superconductors, Rb 3C60 has the second highest superconducting transition temperature, with Tc ) 28 K, which suggests that the Tc of a superconducting (NH 4)3C60 couldbe higher than yet achieved for C60 superconductors, of which Cs 3C60(s) has the highest Tc of 40 K. There is a 28% relative mass change when the NH4 countercation is replaced by ND4, which is a much larger relative change than can be achieved with the alkali metal atoms, which is important for study of the isotopic substitution effect on Tc. There is also the possibility of unique dynamics in which the ammonium ion rotates in the lattice; the presence of a molecular ion, rather than an atomic ion, could play a role in the mechanism of superconductivity, if the solid is superconducting. Finally, alternative methods to produce such an ammonium salt of C 60, such as electrosynthesis or direct synthesis in liquid ammonia, would be required in contrast to the method of the production of M3C60 (M ) alkali atom) based on vapor phase transport of M via sublimation in sealed tubes.