Suboxides and Other Low‐Valent Species

Simon, Arndt

doi:10.1002/9783527691036.hsscvol1007

Cited by 2 publications

(7 citation statements)

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“…The color of Cs gradually darkens to bronze, while that of Rb changes to copper red. 1 Such a color change can be attributed to the formation of suboxides, which are sometimes called a metalrich, electron-rich, or low-valent (subvalent) compound. The evidence for the suboxide formation of heavy alkali metals dates back to an early 1909 study by Rengade, 2 which was followed by extensive studies conducted by Simon and coworkers.…”

Section: Introductionmentioning

confidence: 99%

“…Those of K may exist, but they remain to be characterized. 1 This seems due to the high instability of their suboxide phases or the significant stability of their normal oxide phases, namely Li 2 O, Na 2 O, and K 2 O, in comparison to the suboxides. 11 For Rb, two stable suboxide phases have been identified: Rb 9 O 2 12,13 and Rb 6 O; 5,14 yet an intermediate unstable crystalline compound, Rb 6.33 O (Rb 19 O 3 ), is also known.…”

Section: Introductionmentioning

confidence: 99%

“…They react with oxygen, changing their colors. The color of Cs gradually darkens to bronze, while that of Rb changes to copper red . Such a color change can be attributed to the formation of suboxides, which are sometimes called a metal-rich, electron-rich, or low-valent (subvalent) compound.…”

Section: Introductionmentioning

confidence: 99%

“…Such a color change can be attributed to the formation of suboxides, which are sometimes called a metal-rich, electron-rich, or low-valent (subvalent) compound. The evidence for the suboxide formation of heavy alkali metals dates back to an early 1909 study by Rengade, which was followed by extensive studies conducted by Simon and co-workers. ,− The history of these compounds is summarized in his review articles. ,− …”

Section: Introductionmentioning

confidence: 99%

“…The suboxides of Li and Na have not been synthesized so far. Those of K may exist, but they remain to be characterized . This seems due to the high instability of their suboxide phases or the significant stability of their normal oxide phases, namely Li 2 O, Na 2 O, and K 2 O, in comparison to the suboxides .…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Study on the Electronic Structure of Heavy Alkali-Metal Suboxides

2020

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On the metal-rich side of the phase diagrams of the Rb–O, Cs–O, and Rb–Cs–O systems, one can find a variety of stoichiometries: for example, Rb9O2, Rb6O, Cs4O, Cs7O, Cs11O3, RbCs11O3, and Rb7Cs11O3. They may be termed heavy alkali-metal suboxides. The application of the standard electron-counting scheme to these compounds suggests the presence of surplus electrons. This motivated us to carry out a theoretical study using the first-principles density functional theory (DFT) method. The structures of these compounds are based on either a formally cationic Rb9O2 or Cs11O3 cluster. The analyses of the partial charge density just below the Fermi level and the electron localization function (ELF) have revealed that there exist surplus electrons in interstitial regions of all the investigated suboxides so that the excess positive charge of the cluster can be compensated. Density of states (DOS) calculations suggest that all of the compounds are metallic. Therefore, the suboxides listed above may be regarded as a new family of metallic electrides, where coreless electrons reside in interstitial spaces and provide a conduction channel. Except for the phases of Rb9O2 and Cs11O3, the suboxide structures include both the cationic clusters and alkali-metal matrix. Several charge analyses indicate that the interstitial surplus-electron density can be assigned to the alkali-metal atoms in the metal matrix, leading to the possibility of the presence of negatively charged alkali-metal atoms, namely Rb– (rubidide) and Cs– (caeside) ions, a.k.a. alkalides. In Rb6O, Rb–, Rb0, and Rb+ are found to coexist in the same crystal structure. Similarly, in Cs7O, one can find the three types of Cs atoms. However, in Cs4O, no Cs0 state is identified. In the Rb–Cs–O ternary suboxides, Rb takes a negatively charged anion state or neutral state, while all of the Cs atoms are found to be cationic because they get involved in the Cs11O3 cluster and all the Rb atoms exist in interstitial sites. Orbital interactions between the clusters are analyzed to understand how the condensation of the clusters into the solid happens and how the electride nature ensues. These clusters are found to have some superatomic character.

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Section: Introductionmentioning

confidence: 99%