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二价银化合物超导电性的探索：预测后8年
Quest for Superconductivity in Compounds of Divalent Silver: 8 Years after the Prediction |
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| 课程网址: |
http://videolectures.net/kolikviji_grochala_qsc/
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| 主讲教师: |
Wojciech R. Grochala
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| 开课单位: |
华沙大学
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| 开课时间: |
2009-10-14
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| 课程语种: |
英语
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| 中文简介: |
氟是所有化学键形成元素中最具电负性的。因此，绝大多数二元和更高级无机氟化物是高熔点大带隙电子绝缘体，它们在电磁波谱的可见区域是透明的。已知稀有金属氟化物的例子，但F的价轨道在这些化合物中略微参与电子传输。在这篇文章中，我们描述了最近的理论驱动尝试，将一族TM氟化物转变为一类新型的高温超导体。需要大量混合F的2p轨道和金属价态函数（'共价'）以及部分带占据来产生带交叉，判断出负责异常强烈的电子耦合和超导的出现。这种前提条件满足二价银 - 氟代物（II）的不寻常氟化物。这些迷人的材料与Cu（I）的氧化物有许多共同的特征。不幸的是，在所有已知的银（II）的层状氟化物中，银的未配对的d电子是铁磁性的。这与未掺杂的oxocuprate观察到的反铁磁有序相反。在该描述中，将描述氟代物（II）的晶体工程，其靶向超导体的层状反铁磁性前体。
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| 课程简介: |
Fluorine is the most electronegative among all chemical bond–forming elements. Because of this, the vast majority of binary and higher inorganic fluorides are high–melting large–band gap electronic insulators, which are transparent in the visible region of the electromagnetic spectrum. Rare examples of metallic fluorides are known, but valence orbitals of F marginally participate in the electronic transport in these compounds. In this account we describe recent theory–driven attempts to turn a family of TM fluorides into a novel class of high–temperature superconductors. Substantial mixing of F’s 2p orbitals and metal valence functions (‘covalence’) as well as partial band occupation are needed to generate band crossing judged responsible for unusually strong vibronic coupling and for the appearance of superconductivity. This precondition is satisfied for unusual fluorides of divalent silver – fluoroargentates (II). These fascinating materials share lots of common features with oxides of Cu(I). Unfortunately, in all known layered fluorides of silver (II) the unpaired d electrons of silver order ferromagnetically. This is in contrast to antiferromagnetic ordering observed for undoped oxocuprates. In this account attempts will be described of crystal-engineering of fluoroargentates (II) which target a layered antiferromagnetic precursor of a superconductor.
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| 关 键 词: |
电负性; 无机氟化物; 电子绝缘体
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| 课程来源: |
视频讲座网
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| 最后编审: |
2019-05-11：cwx
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| 阅读次数: |
50
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