Superatomic crystal emerging in transition-metal oxides: Molybdenum hollandite K<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Mo<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>8</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>16</mml:mn></mml:msub></mml:math>

Toriyama, T.; Watanabe, Mizuki; Konishi, Toshifumi; Ohta, Y.

doi:10.1103/physrevb.88.235116

Cited by 6 publications

(9 citation statements)

References 31 publications

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“…This result indicates that the insulating nature of the FI phase originates from the formation of Cr tetramers in the four-chain columns, not from the Cr-Cr dimers in the double chains. This feature is quite different from the case in K 2 Mo 8 O 16 , for which the insulating gap was reported to arise from the distortions in the double chain of the edge-shared MoO 6 octahedra [24].…”

Section: (B)] Which Indicatesmentioning

confidence: 83%

“…This feature is quite different from the case in K 2 Mo 8 O 16 , for which the insulating gap was reported to arise from the distortions in the double-chain of the edge-shared MoO 6 octahedra. 24 We also checked the roles of the Coulomb correlation U and the Peierls dimerization in the MIT and the structural transition. To investigate the U effect in the FM phase, the charge density difference (CDD) between the GGA+U and GGA calculations is plotted in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Structural instability and the Mott-Peierls transition in a half-metallic hollandite :K2Cr8O16

Kim

Min

2014

Phys. Rev. B

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In order to explore the driving mechanism of the concomitant metal-insulator and structural transitions in quasi-one-dimensional hollandite K 2 Cr 8 O 16 , electronic structures and phonon properties are investigated by employing the ab initio density functional theory (DFT) calculations. We have found that the imaginary phonon frequency reflecting the structural instability appears only in the DFT + U (U : Coulomb correlation) calculation, which indicates that the Coulomb correlation plays an essential role in the structural transition. The lattice displacements of the softened phonon at X explain the observed lattice distortions in K 2 Cr 8 O 16 perfectly well, suggesting the Peierls distortion vector Q of X (0, 0, 1/2). The combined study of electronic and phonon properties reveals that half-metallic K 2 Cr 8 O 16 , upon cooling, undergoes the correlation-assisted Peierls transition to become a Mott-Peierls ferromagnetic insulator at low temperature.

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Section: (B)] Which Indicatesmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Structural instability and the Mott-Peierls transition in a half-metallic hollandite :K2Cr8O16

Kim

Min

2014

Phys. Rev. B

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“…The difference in the Mo-Mo bond length reaches about 20%, as large as in MoO 2 , which makes it easy and meaningful to identify the "molecules" in the lattice. The electronic state of K 2 Mo 8 O 16 has been approximated as a solid of "superatoms" of the Mo tetramers, and thus is considered as an MOC in analogy of molecular crystals made of organic molecules [131]. Similar Mo tetramers are observed in a related compound Rb 1.5 Mo 8 O 16 , which shows a semiconductor-like resistivity governed by cluster-to-cluster electron hopping at high temperatures and becomes more insulating below 208 K [132].…”

Section: Molecular Orbital Crystalsmentioning

confidence: 99%

Structural instability of the rutile compounds and its relevance to the metal–insulator transition of VO2

Hiroi

2015

Progress in Solid State Chemistry

103

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The metal-insulator transition (MIT) of VO 2 is discussed with particular emphasis on the structural instability of the rutile compounds toward dimerization. Ti substitution experiments reveal that the MIT is robust up to 20% Ti substitutions and occurs even in extremely thin V-rich lamellas in spinodally decomposed TiO 2 -VO 2 composites, indicating that the MIT is insensitive to hole doping and essentially takes on a local character. These observations suggest that either electron correlation in the Mott-Hubbard sense or Peierls (Fermi-surface) instability plays a minor role on the MIT. Through a broad perspective of crystal chemistry on the rutile-related compounds, it is noted that VO 2 and another MIT compound NbO 2 in the family eventually lie just near the borderline between the two structural groups with the regular rutile structure and the distorted structures characterized by the formation of dimers with direct metal-metal bonding. It is also shown that the two compounds of the rutile form do not follow the general trends in structure observed for the other rutile compounds, giving clear evidence of an inherent structural instability present in the two compounds. The MITs of VO 2 and NbO 2 are natural consequences of structural transitions between the two groups, as all the d electrons are trapped in the bonding molecular orbitals of dimers at low temperatures. Such dimer crystals are ubiquitously found in early transition metal compounds having chain-like structures, such as MoBr 3 , NbCl 4 , Ti 4 O 7 , and V 4 O 7 , the latter two of which also exhibit MITs probably of the same origin. In a broader sense, the dimer crystal is a kind of "molecular orbital crystals" in which virtual molecules made of transition metal atoms with partially-filled t 2g shells, such as dimers, trimers or larger ones, are generated by metal-metal bonding and are embedded into edge-or face-sharing octahedron networks of various kinds. The molecular orbital crystallization opens a natural route to stabilization of unpaired t 2g electrons in crystals.2

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“…This enables several possible applications in thermochromics [19,20], non-volatile memory [21], and phase change materials [5,[22][23][24][25]. Moreover, by arranging additional spins in the molecular orbital, exotic magnetic materials, called cluster magnets, can be obtained [26][27][28][29][30][31][32][33][34][35].…”

mentioning

confidence: 99%

“…The hollandite-type K 2 Mo 8 O 16 is another example, comprising molybdenum tetramer clusters with a spin S = 1/2. Despite the strong antiferromagnetic interaction with the Weiss temperature of -34 K, the long-range ordering is suppressed to 2 K, expecting us a realization of spin-liquid like state [28,29].…”

mentioning

confidence: 99%

Robust atomic orbital in the cluster magnet LiMoO2

Katayama,

Takeda,

Yamaguchi

et al. 2020

Preprint

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Superatomic crystal emerging in transition-metal oxides: Molybdenum hollandite K2Mo8O16

Cited by 6 publications

References 31 publications

Structural instability and the Mott-Peierls transition in a half-metallic hollandite :K2Cr8O16

Structural instability and the Mott-Peierls transition in a half-metallic hollandite :K2Cr8O16

Structural instability of the rutile compounds and its relevance to the metal–insulator transition of VO2

Robust atomic orbital in the cluster magnet LiMoO2

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