Single Crystal Growth of the High Pressure Phase of (VO)2P2O7 at 3 GPa

Saito, Takashi; Terashima, Taichi; Azuma, Masaki; Takano, Mikio; Goto, T.; Ohta, Hiromichi; Utsumi, Wataru; Bordet, Pierre; Johnston, D. C.

doi:10.1006/jssc.2000.8761

Cited by 42 publications

(41 citation statements)

References 20 publications

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“…Comparing with the experimental results, 8 we found that our calculated J OPO deviates from the experimental value (J OPO = À131.6 K) by 19.1%. This is probably partly due to the limitations of DFT, but it may arise from the use of a one-dimensional model to extract J from the experiments, ignoring the interlayer (19.2 K) and interchain couplings (2.8 K), which may influence the intrachain couplings.…”

Section: -O(2)-p-o(2)-provides a Better Exchange Pathway Than -O(3)-isupporting

confidence: 59%

“…2) shows a direct band gap of 3.61 eV at the X point of the Brillouin zone, which is qualitatively consistent with the experimental observation. The color is observed to be transparent green, 8 suggesting a band gap larger than 1.8 eV. In contrast, DFT calculations at the PW91 and LDA level give much smaller band gaps of 0.81 and 0.48 eV, respectively.…”

Section: Electronic Structure Of Vopomentioning

confidence: 95%

“…Since DFT may lead to small systematic errors in determining the equilibrium geometries that might induce systematic changes in the spin exchange coupling, which are very sensitive to geometry, we used the experimental cell parameters and atomic positions 8 in all studies of the VOPO magnetic and electronic structure, unless specifically stated otherwise.…”

Section: Computational Detailsmentioning

confidence: 99%

“…We also found that the optimum spin coupling configuration is antiferromagnetic (AFM) along the chains (a axis), while the coupling is ferromagnetic (FM) between the chains along the b and c axis, consistent with experimental results. 5,8 The Mulliken charge of VOPO shows that the most nucleophilic site is O(3) (À1.08 e À ), followed by O(2) (À0.93 e À ), O(2 0 ) (À0.91 e À ), and then O(1) (À0.76 e À ). The larger magnitude for O(3) is expected, since it has a double bond to phosphorus and two electropositive vanadium neighbors.…”

Section: Electronic Structure Of Vopomentioning

confidence: 99%

“…Subsequently, Saito et al showed that at high pressure VOPO leads to a higher symmetry structure with only a single chain (one spin gap). 8 From magnetic susceptibility measurements over the range 2-300 K, they were able to deduce the J OPO and J O spin couplings using the assumption that both couplings were temperature-independent. 8 There have been no previous computational attempts to evaluate the spin couplings of VOPO using the threedimensional crystal structure.…”

Section: Introductionmentioning

confidence: 99%

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The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

Cheng

Nielsen

Tahir-Kheli

et al. 2011

Phys. Chem. Chem. Phys.

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We have studied the magnetic structure of the high symmetry vanadyl pyrophosphate ((VO) 2 P 2 O 7 , VOPO), focusing on the spin exchange couplings, using density functional theory (B3LYP) with the full three-dimensional periodicity. VOPO involves four distinct spin couplings: two larger couplings exist along the chain direction (a-axis), which we predict to be antiferromagnetic, J OPO = À156.8 K and J O = À68.6 K, and two weaker couplings appear along the c (between two layers) and b directions (between two chains in the same layer), which we calculate to be ferromagnetic, J layer = 19.2 K and J chain = 2.8 K. Based on the local density of states and the response of spin couplings to varying the cell parameter a, we found that J OPO originates from a super-exchange interaction through the bridging -O-P-O-unit. In contrast, J O results from a direct overlap of 3d x 2 À y 2 orbitals on two vanadium atoms in the same V 2 O 8 motif, making it very sensitive to structural fluctuations. Based on the variations in V-O bond length as a function of strain along a, we found that the V-O bonds of V-(OPO) 2 -V are covalent and rigid, whereas the bonds of V-(O) 2 -V are fragile and dative. These distinctions suggest that compression along the a-axis would have a dramatic impact on J O , changing the magnetic structure and spin gap of VOPO. This result also suggests that assuming J O to be a constant over the range of 2-300 K whilst fitting couplings to the experimental magnetic susceptibility is an invalid method. Regarding its role as a catalyst, the bonding pattern suggests that O 2 can penetrate beyond the top layers of the VOPO surface, converting multiple V atoms from the +4 to +5 oxidation state, which seems crucial to explain the deep oxidation of n-butane to maleic anhydride.

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Section: -O(2)-p-o(2)-provides a Better Exchange Pathway Than -O(3)-isupporting

confidence: 59%

Section: Electronic Structure Of Vopomentioning

confidence: 95%

Section: Computational Detailsmentioning

confidence: 99%

Section: Electronic Structure Of Vopomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

Cheng

Nielsen

Tahir-Kheli

et al. 2011

Phys. Chem. Chem. Phys.

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High frequency ESR measurements of high pressure phase SiCo ₂ O ₄

Zhang

Okubo

Ohta

et al. 2006

Phys. Status Solidi (c)

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New Co spinel compound SiCo 2 O 4 have been synthesized by using the high-pressure synthesis technique. High frequency ESR measurements of powder samples of SiCo 2 O 4 have been performed by using the pulsed magnetic field up to 16 T in the frequency range from 60 GHz to 540 GHz. From the frequencyfield diagram at 1.8 K two critcal field resonances are observed at 1.7 T, which correspond to the field of the metamagnetic transition and 2.3 T. The g-values are estimated to be 6.7 and 4.5 from the ESR mode in the field induced ferromagnet phase.

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Ultrasonics in Low Dimensional Spin and Electronic Peierls-Systems

2007

Springer Series in Solid-State Sciences

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Single Crystal Growth of the High Pressure Phase of (VO)2P2O7 at 3 GPa

Cited by 42 publications

References 20 publications

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

High frequency ESR measurements of high pressure phase SiCo ₂ O ₄

Ultrasonics in Low Dimensional Spin and Electronic Peierls-Systems

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Single Crystal Growth of the High Pressure Phase of (VO)2P2O7 at 3 GPa

Cited by 42 publications

References 20 publications

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

High frequency ESR measurements of high pressure phase SiCo 2 O 4

Ultrasonics in Low Dimensional Spin and Electronic Peierls-Systems

Contact Info

Product

Resources

About

High frequency ESR measurements of high pressure phase SiCo ₂ O ₄