Electron spectrometry at the µeV level and the electron affinities of Si and F

Blondel, Christophe; Delsart, C.; Goldfarb, Fabienne

doi:10.1088/0953-4075/34/9/101

Cited by 185 publications

(124 citation statements)

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“…24 The ionization energy and electron affinity of Li and F are 5.39 and In all but the rinsed, discharged sample ͑127D _ rinsed͒ a broad peak is seen at approximately 18 ppm, which corresponds to the chemical shift of the anion receptor salt, suggesting at least partial co-intercalation of the anion receptor. −3.40 eV, 25,26 respectively ͑the values calculated in this work were 5.62 and −3.54 eV, respectively͒. The solvation of Li + and F − in PC were calculated to be −135.16 and −94.36 kcal/mol.…”

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confidence: 52%

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

West

Whitacre

Leifer

et al. 2007

J. Electrochem. Soc.

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We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and 11 B nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties. As cathodes in lithium batteries, carbon-fluoride ͑C-F͒ compounds offer very high theoretical specific capacity, on the scale of 1785 mAh/g for C 1.25 F, though to date, all C-F compounds regardless of preparation conditions are strictly non-rechargeable. A rechargeable C-F cathode would be very desirable in terms of specific energy relative to conventional lithium-ion transition metal oxide cathodes, though there are numerous difficulties associated with reversible fluorination of carbon which relate to a large extent to the nature of the C-F bond.The reaction of carbon and fluorine is well known to yield a wide range of useful compounds with varying properties, depending on preparation conditions and synthesis route. Many of these compounds, despite their relatively poor electronic conductivity, are useful as cathodes for primary Li batteries. Direct reaction of fluorine gas with graphite at temperatures greater than 350°C results in covalent bonding of C x -F with the transition of the planar sp 2 graphene sheets to buckled sp 3 carbon, and concomitant drop in electrical conductivity with decreasing x. Room temperature chemical fluorination of graphite in the presence of various fluorides such as HF, WF 6 , SbF 5 , and IF 5 has been demonstrated by others up to C 1.0 F 0.89 ͑I 0.02 H 0.06 ͒. 1 Under these preparation conditions, the sp 2 carbon hybridization is maintained, and the C-F bonding is ionic. Electrochemical fluorination of graphite in aqueous or anhydrous HF media is also possible, resulting in ionic or semi-covalent C x -F depending on the degree of fluorination, though this process is not significantly reversible and has poor Coulombic efficiency. 2-4 A candidate rechargeable C-F cathode must retain good electronic conductivity and thus the practical lower bound on C x F is likely near the C-F delocalizati...

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confidence: 52%

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

West

Whitacre

Leifer

et al. 2007

J. Electrochem. Soc.

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“…These EAs are comparable to the CCSD + F12 + "high level correction" value (3.4276 eV) 41 and the experimental value (3.401 eV). 42 Table 1 Conformations of Si 2 H 4 . As a result of the relative weakness of silicon π-bonds, unsaturated silicon hydrides have many physical dissimilarities compared to analogous hydrocarbons.…”

Section: ■ Resultsmentioning

confidence: 99%

Assessment of Perturbative Explicitly Correlated Methods for Prototypes of Multiconfiguration Electronic Structure

Roskop

Kong

Valeev

et al. 2013

J. Chem. Theory Comput.

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The performance of the [2]S and [2]R12 universal perturbative corrections that account for one-and manybody basis set errors of single-and multiconfiguration electronic structure methods is assessed. A new formulation of the [2]R12 methods is used in which only strongly occupied orbitals are correlated, making the approach more amenable for larger computations. Three model problems are considered using the aug-ccpVXZ (X = D,T,Q) basis sets: the electron affinity of fluorine atom, a conformational analysis of two Si2H4structures, and a description of the potential energy surfaces of the X 1Σg+, a 3Πu, b 3Σg-, and A1Πu states of C2. In general, the [2]R12 and [2]S corrections enhance energy convergence for conventional multireference configuration interaction (MRCI) and multireference perturbation theory (MRMP2) calculations compared to their complete basis set limits. For the electron affinity of the F atom, [2]R12 electron affinities are within 0.001 eV of the experimental value. The [2]R12 conformer relative energy error for Si2H4 is less than 0.1 kcal/mol compared to the complete basis set limit. The C2 potential energy surfaces show nonparallelity errors that are within 0.7 kcal/mol compared to the complete basis set limit. The perturbative nature of the [2]R12 and [2]S methods facilitates the development of a straightforward textbased data exchange standard that connects an electronic structure code that can produce a two-particle density matrix with a code that computes the corrections. This data exchange standard was used to implement the interface between the GAMESS MRCI and MRMP2 codes and the MPQC methods is used in which only strongly occupied orbitals are correlated, making the approach more amenable for larger computations. Three model problems are considered using the aug-cc-pVXZ (X = D,T,Q) basis sets: the electron affinity of fluorine atom, a conformational analysis of two Si 2 H 4 structures, and a description of the potential energy surfaces of the X 1 Σ g + , a 3 Π u , b 3 Σ g -, and A 1 Π u states of C 2 . In general, the [2] R12 and [2] S corrections enhance energy convergence for conventional multireference configuration interaction (MRCI) and multireference perturbation theory (MRMP2) calculations compared to their complete basis set limits. For the electron affinity of the F atom, [2] R12 electron affinities are within 0.001 eV of the experimental value. The [2] R12 conformer relative energy error for Si 2 H 4 is less than 0.1 kcal/mol compared to the complete basis set limit. The C 2 potential energy surfaces show nonparallelity errors that are within 0.7 kcal/mol compared to the complete basis set limit. The perturbative nature of the [2] R12 and [2] S methods facilitates the development of a straightforward text-based data exchange standard that connects an electronic structure code that can produce a two-particle density matrix with a code that computes the corrections. This data exchange standard was used to implement the interface between the GAMESS MRCI and MRMP2 codes and t...

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“…0.1−0.2 eV. First, although it is not accurate to equate an AE 298 to the enthalpy of the corresponding unimolecular reaction at 298 K because of thermal effects, 26 28 In calculations for F − , we use the value of −249 using the electron affinity (EA) reported by Blondel et al, 29 and for F 2 − , the value of −301 which uses the EA reported by Artau et al 30 The values used for Cl − , Br − and I − are −227, −213, and −188, respectively, which use experimental EAs from a recent review paper. 31 For CF − we use a value of −63, using the EA(CF) = 3.3 ± 1.1 eV (reported as a lower limit), 32 and for CF 2 − a value of −199 which uses the EA(CF 2 ) = 0.179 ± 0.005 eV.…”

Section: Thermochemistry: General Commentsmentioning

confidence: 99%