Donor-anion interactions at the charge localization and charge ordering transitions of (TMTTF)(2)AsF6 probed by NEXAFS
Medjanik, Katerina LU ; Chernenkaya, A. ; Nepijko, S. A. ; Öhrwall, Gunnar LU
; Foury-Leylekian, P.
; Alemany, P.
; Canadell, E.
; Schoenhense, G.
and Pouget, J. -P.
(2015)
In Physical Chemistry Chemical Physics
17(29).
p.19202-19214
- Abstract
- 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)(2)AsF6 were performed from room temperature (RT) to 90 K, allowing to reach the charge localization regime below T-rho approximate to 230 K and to cross the charge ordering (CO) transition at T-CO approximate to 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... (More)
- 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)(2)AsF6 were performed from room temperature (RT) to 90 K, allowing to reach the charge localization regime below T-rho approximate to 230 K and to cross the charge ordering (CO) transition at T-CO approximate to 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 donor...anion 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 S...F 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. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/7779616
- author
- Medjanik, Katerina
LU
; Chernenkaya, A.
; Nepijko, S. A.
; Öhrwall, Gunnar
LU
; Foury-Leylekian, P.
; Alemany, P.
; Canadell, E.
; Schoenhense, G.
and Pouget, J. -P.
- organization
- publishing date
- 2015
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physical Chemistry Chemical Physics
- volume
- 17
- issue
- 29
- pages
- 19202 - 19214
- publisher
- Royal Society of Chemistry
- external identifiers
-
- pmid:26135020
- wos:000358207400035
- scopus:84937231547
- pmid:26135020
- ISSN
- 1463-9084
- DOI
- 10.1039/c5cp02902c
- language
- English
- LU publication?
- yes
- id
- 6da5ee23-210a-4db4-a6e6-43a67138a355 (old id 7779616)
- date added to LUP
- 2016-04-01 14:58:51
- date last changed
- 2022-04-14 20:35:35
@article{6da5ee23-210a-4db4-a6e6-43a67138a355,
abstract = {{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)(2)AsF6 were performed from room temperature (RT) to 90 K, allowing to reach the charge localization regime below T-rho approximate to 230 K and to cross the charge ordering (CO) transition at T-CO approximate to 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 donor...anion 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 S...F 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.}},
author = {{Medjanik, Katerina and Chernenkaya, A. and Nepijko, S. A. and Öhrwall, Gunnar and Foury-Leylekian, P. and Alemany, P. and Canadell, E. and Schoenhense, G. and Pouget, J. -P.}},
issn = {{1463-9084}},
language = {{eng}},
number = {{29}},
pages = {{19202--19214}},
publisher = {{Royal Society of Chemistry}},
series = {{Physical Chemistry Chemical Physics}},
title = {{Donor-anion interactions at the charge localization and charge ordering transitions of (TMTTF)(2)AsF6 probed by NEXAFS}},
url = {{http://dx.doi.org/10.1039/c5cp02902c}},
doi = {{10.1039/c5cp02902c}},
volume = {{17}},
year = {{2015}},
}