Characterization of the anion-ordering transition in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>TMTTF</mml:mi><mml:msub><mml:mo>)</mml:mo><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>ReO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>by x-ray absorption and photoemission spectroscopies

Subı́as, G.; Abbaz, Tahar; Fabre, J.M.; Fraxedas, Jordi

doi:10.1103/physrevb.76.085103

Cited by 9 publications

(6 citation statements)

References 38 publications

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“…). This assignment is very similar to that proposed for TMTTF 2 ReO 4 , 33 the only difference lying in the assignment of the two upper peaks. In the present case, when comparing the band structure and the DOS, it is clear that the upper peak originates from only two bands which are the in-phase and out-of-phase combinations of the upper b 2u TMTTF molecular orbital (there are two bands associated to this orbital because the unit cell contains two TMTTF donors).…”

Section: B Sulfur L-edge Nexafssupporting

confidence: 84%

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS

Medjanik

Chernenkaya

Nepijko

et al. 2015

Phys. Chem. Chem. Phys.

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High-resolution near-edge X-ray absorption fine structure (NEXAFS) measurements at the As M-edge, F K-edge and S L-edge of the Fabre salt (TMTTF)2AsF6 were performed from room temperature (RT) to 90 K, allowing to reach the charge localization regime below Tρ ≈ 230 K and to cross the charge ordering (CO) transition at TCO ≈ 102 K. The F K-edge and S L-edge spectra exhibit several transitions which have been indexed on the basis of first-principles DFT calculations. Upon cooling from RT significant energy shifts up to +0.8 eV and -0.4 eV were observed in transitions exhibited by the F 1s and S 2p spectra respectively, while the As 3p doublet does not show a significant shift. Opposite energy shifts found in the F 1s and S 2p spectra reflect substantial thermal changes in the electronic environment of F atoms of the anion and S atoms of TMTTF. The changes found around the charge localization crossover suggest an increase of the participation of the S d orbitals in the empty states of TMTTF as well as an increase of the strength of donoranion interactions. A new F 1s pre-edge signal detected upon entry into the CO phase is a clear fingerprint of the symmetry breaking occurring at TCO. We propose that this new transition is caused by a substantial mixing between the HOMO of the AsF6(-) anion and the unoccupied part of the TMTTF HOMO conduction band. Analysis of the whole spectra also suggests that the loss of the inversion symmetry associated with the CO is due to an anion displacement increasing the strength of SF interactions. Our data show unambiguously that anions are not, as previously assumed, innocent spectators during the electronic modifications experienced by the Fabre salts upon cooling. In particular the interpretation of the spectra pointing out a thermally dependent mixing of anion wave functions with those of the TMTTF chains demonstrates for the first time the importance of anion-donor interactions.

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Section: B Sulfur L-edge Nexafssupporting

confidence: 84%

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS

Medjanik

Chernenkaya

Nepijko

et al. 2015

Phys. Chem. Chem. Phys.

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“…In addition, the N1s line shows three components at 398.0, 399.5, and 401.4 eV, respectively. Similar results were obtained for (TMTTF) 2 PF 6 [24], (TMTSF) 2 PF 6 [37], and (TMTTF) 2 ReO 4 [38] single crystals, where TMTTF and TMTSF stand for tetramethyltetrathiafulvalene and tetramethyltetraselenafulvalene, respectively, and on thin films of TTF-TCNQ grown by vacuum sublimation for the N1s lines, with binding energies of 398.0 and 399.8 eV, respectively, for the most prominent features [39].…”

Section: Charge Transfer In Nanoparticles Of Ttf-tcnqsupporting

confidence: 78%

Characterization of Charge States in Conducting Organic Nanoparticles by X-ray Photoemission Spectroscopy

et al. 2021

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The metallic and semiconducting character of a large family of organic materials based on the electron donor molecule tetrathiafulvalene (TTF) is rooted in the partial oxidation (charge transfer or mixed valency) of TTF derivatives leading to partially filled molecular orbital-based electronic bands. The intrinsic structure of such complexes, with segregated donor and acceptor molecular chains or planes, leads to anisotropic electronic properties (quasi one-dimensional or two-dimensional) and morphology (needle-like or platelet-like crystals). Recently, such materials have been synthesized as nanoparticles by intentionally frustrating the intrinsic anisotropic growth. X-ray photoemission spectroscopy (XPS) has emerged as a valuable technique to characterize the transfer of charge due to its ability to discriminate the different chemical environments or electronic configurations manifested by chemical shifts of core level lines in high-resolution spectra. Since the photoemission process is inherently fast (well below the femtosecond time scale), dynamic processes can be efficiently explored. We determine here the fingerprint of partial oxidation on the photoemission lines of nanoparticles of selected TTF-based conductors.

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“…Structural refinements on (TMTTF) 2 ReO 4 revealed the staggered orientation of the anions along the [111]-direction and the tetramerization with intra-stack distances [70]. The molecular tetramerization was also observed by angular-dependent X-ray near-edge structure (XANES) measurements [27]; in addition, they reveal a slight shift and deformation of the ReO 4 anions. For all salts with tetrahedral anions X = BF 4 , ClO 4 and ReO 4 , electron spin resonance (ESR) spectroscopy sees a drop of the spin susceptibility right at T AO that is attributed to the formation of a singlet-triplet gap upon tetramerization [71][72][73].…”

Section: Anion Ordermentioning

confidence: 85%

“…The alternating orientation of the tetrahedra along and perpendicular to the stacks leads to a doubling of the lattice periodicity; hence the anion order is a structural transition with wave vector q AO = ( 1 2 , 1 2 , 1 2 ). X-ray absorption near edge structure (XANES or NEXAFS) [27] and infrared optical spectroscopy [23] measurements unanimously identify a tetramerization of the TMTTF stacks at the AO transition T AO , the latter also providing evidence for a 0110 charge pattern. A scheme of the corresponding modification of the structure and the charge pattern is shown in Figure 2e.…”

Section: Structural Considerationsmentioning

confidence: 99%

Structural and Electronic Properties of (TMTTF)2X Salts with Tetrahedral Anions

et al. 2018

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Comprehensive measurements of the pressure-and temperature-dependent dc-transport are combined with dielectric spectroscopy and structural considerations in order to elucidate the charge and anion orderings in the quasi-one-dimensional charge-transfer salts (TMTTF) 2 X with non-centrosymmetric anions X = BF 4 , ClO 4 and ReO 4. Upon applying hydrostatic pressure, the charge-order transition is suppressed in all three compounds, whereas the influence on the anion order clearly depends on the particular compound. A review of the structural properties paves the way for understanding the effect of the anions in their methyl cavities on the ordering. By determining the complex dielectric constantˆ (ω, T) in different directions we obtain valuable information on the contribution of the anions to the dielectric properties. For (TMTTF) 2 ClO 4 and (TMTTF) 2 ReO 4 , b exhibits an activated behavior of the relaxation time with activation energies similar to the gap measured in transport, indicating that the relaxation dynamics are determined by free charge carriers.

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Characterization of the anion-ordering transition in(TMTTF)2ReO4by x-ray absorption and photoemission spectroscopies

Cited by 9 publications

References 38 publications

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS

Characterization of Charge States in Conducting Organic Nanoparticles by X-ray Photoemission Spectroscopy

Structural and Electronic Properties of (TMTTF)2X Salts with Tetrahedral Anions

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Characterization of the anion-ordering transition in(TMTTF)2ReO4by x-ray absorption and photoemission spectroscopies

Cited by 9 publications

References 38 publications

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)2AsF6 probed by NEXAFS

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)2AsF6 probed by NEXAFS

Characterization of Charge States in Conducting Organic Nanoparticles by X-ray Photoemission Spectroscopy

Structural and Electronic Properties of (TMTTF)2X Salts with Tetrahedral Anions

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Product

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Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS

Donor–anion interactions at the charge localization and charge ordering transitions of (TMTTF)₂AsF₆ probed by NEXAFS