On the MoO2 Structure Type.

Magnéli, Arne; Andersson, Georg; Sundkvist, Gustav

doi:10.3891/acta.chem.scand.09-1378

Cited by 167 publications

(79 citation statements)

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“…A structural transition takes place simultaneously from the high-temperature rutile structure ( Fig. 1) to the low-temperature monoclinic structure called M1, which is characterized by the formation of V-V pairs slightly tilted from the c axis [17][18][19].…”

Section: Mits In Vo 2 and Related Compoundsmentioning

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

100

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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Section: Mits In Vo 2 and Related Compoundsmentioning

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

100

103

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“…6 Other oxides, like α-ReO2 and a low-temperature form of VO2, adopt the same structure type. 3 Reports on tetragonal rutile-type variants (space group P42/mnm) of α-MoO2 and α-WO2, one from 1926 by Goldschmidt et al 1 and a second one regarding the molybdenum dioxide from 2004 by Seisenbaeva et al,7 are rare. Simulated diffraction patterns indicate that a very good instrumental resolution is necessary to distinguish between monoclinic and tetragonal rutile variants.…”

Section: Introductionmentioning

confidence: 99%

“…Many binary oxides are known for both elements, but only the di-and trioxides have the element in just one oxidation state (+IV / +VI). MoO2 [1][2][3][4][5] and WO2 1,2,5 (from now on, we will call those compounds α-MoO2 and α-WO2) crystallize isotypically in the monoclinic space group P21/c. MoO2 is the eponym for this structure type, which can be described as a distorted rutile type.…”

Section: Introductionmentioning

confidence: 99%

HP-MoO₂: A High-Pressure Polymorph of Molybdenum Dioxide

et al. 2017

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High-pressure molybdenum dioxide (HP-MoO2) was synthesized using a multi-anvil press at 18 GPa and 1073 K, as motivated by previous first-principles calculations. The crystal structure was determined by single-crystal X-ray diffraction. The new polymorph crystallizes isotypically to HP-WO2 in the orthorhombic crystal system in space group Pnma and was found to be diamagnetic. Theoretical investigations using structure optimization at density-functional theory (DFT) level indicate a transition pressure of 5 GPa at 0 K and identify the new compound as slightly metastable at ambient pressure with respect to the thermodynamically stable monoclinic MoO2 (α-MoO2; ΔEm = 2.2 kJ·mol -1 ).

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“…Crystalline phases with 0 < x < 2 have not been observed to MoOg is generally described as having a distorted rutile type stucture [62]. a-MoOg is the most commonly occurring form of MoO^.…”

Section: Structures and Propertiesmentioning

confidence: 99%

Laser photodeposition of molybdenum oxide thin films from organometallic precursors

Olson

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On the MoO2 Structure Type.

Cited by 167 publications

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

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

HP-MoO₂: A High-Pressure Polymorph of Molybdenum Dioxide

Laser photodeposition of molybdenum oxide thin films from organometallic precursors

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On the MoO2 Structure Type.

Cited by 167 publications

References 0 publications

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

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

HP-MoO2: A High-Pressure Polymorph of Molybdenum Dioxide

Laser photodeposition of molybdenum oxide thin films from organometallic precursors

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HP-MoO₂: A High-Pressure Polymorph of Molybdenum Dioxide