Jahn–Teller effect in Ag2+ doped KCl and NaCl: Is there any influence of the host lattice?

Trueba, Alfredo; Garcı́a-Lastra, J. M.; Graaf, Coen de; García‐Fernández, Pablo; Barriuso, M. T.; Aramburu, J. A.; Moreno, M.

doi:10.1016/j.cplett.2006.08.113

Cited by 23 publications

(89 citation statements)

References 14 publications

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“…The present results for NaCl:Ni + are thus fully different from those found for NaCl:Rh 2+11 or KCl:Ag 2+ , 35 where the barrier comes mainly from the anharmonicity. Therefore, in NaCl:Ni + the electronic structure of the impurity plays a key role for understanding the equilibrium geometry.…”

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confidence: 99%

“…As a salient feature, we have found that in all performed calculations the |B| value for NaCl:Ni + is less than 160 cm −1 , thus certainly smaller than the values derived for NaCl:Rh 2+ (B = 511 cm −1 ), 11,13 NaCl:Ag 2+ (B = 500 cm −1 ), or KCl:Ag 2+ (B = 1024 cm −1 ). 35 Values of the equilibrium R eq and R ax distances for both the B 1g and A 1g states and the barrier B derived through representative periodic supercell and cluster calculations are gathered in Tables 1 and 2, respectively. In the case of periodic calculations, most of the values obtained with the best basis set give rise to positive B values in the range 80−120 cm −1 .…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the positive B values obtained in periodic and cluster calculations (Tables 1 and 2) are compatible with this estimation. A central matter in this research is to understand why the B value for NaCl:Ni + is much smaller than those derived for Ag 2+ -doped NaCl and KCl 35 and for NaCl:Rh 2+ . 11,13 To achieve this goal, we have analyzed the results derived for NaCl:Ni + with a 87-ion cluster (Figure 3), giving B = 74 cm −1 (Table 2), by means of the procedure explained in section 3.…”

Section: Inorganic Chemistrymentioning

confidence: 96%

“…For comparison, in NaCl:Ag 2+ , where g ∥ = 2.198 and g ⊥ = 2.041, 16,10 T t = 95 K, while the calculated B value is equal 35 to 500 cm −1 . In KCl:Ag 2+ , whose g tensor is very close to that measured for NaCl:Ag 2+ , it is found 35 that B = 1024 cm −1 , which is consistent with a higher T t = 160 K value. 16 Bearing these facts in mind, the present work is addressed to explore the system NaCl:Ni + by means of ab initio calculations based on density functional theory (DFT), together with an analysis of the results, seeking to clarify the mechanisms responsible for the energy barrier.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

Barriuso¹,

Ortiz-Sevilla²,

Aramburu³

et al. 2013

Inorg. Chem.

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Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn−Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out both periodic and cluster ab initio calculations on the model system NaCl:Ni + . This system is particularly puzzling because, according to experimental data, its barrier is much smaller than that for other d 9 and d 7 ions in similar lattices. All calculations performed on the model system lead, in fact, to values |B| ≤ 160 cm −1 , which are certainly smaller than B = 500 cm −1 derived for NaCl:M 2+ (M = Ag, Rh) or B = 1024 cm −1 obtained for KCl:Ag 2+ . As a salient feature, analysis of calculations carried out as a function of the Q θ (∼3z 2 − r 2 ) coordinate unveils the microscopic origin of the barrier. It is quantitatively proven that the elongated geometry observed for NaCl:Ni + is due to the 3d−4s vibronic admixture, which is slightly larger than the anharmonicity in the e g JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system, contrary to cases where the complex formed by d 9 or d 7 ions is elastically decoupled from the host lattice. Although the magnitude of B for NaCl:Ni + is particularly small, the tunneling splitting, 3Γ, is estimated to be below 9 cm −1 , thus explaining why the coherence is easily destroyed by random strains and thus a static JT effect is observed experimentally. As a main conclusion, the barrier in JT systems cannot be understood neglecting the tiny changes of the electronic density involved in small distortions. The present calculations reasonably explain the experimental g tensor of NaCl:Ni + , pointing out that the d−d transitions in NiCl 6 5− are much smaller than those for CuCl 6 4− and the optical electronegativity of Ni + is only around 1.

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confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

Barriuso¹,

Ortiz-Sevilla²,

Aramburu³

et al. 2013

Inorg. Chem.

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“…2) as demonstrated by EPR data 19,21,23,[36][37] . Along this line theoretical calculations carried out on KCl:Ag 2+ and NaCl:Ag 2+ reveal that the energy difference between compressed and elongated conformations is equal to 127 meV and 62 meV, respectively 53 . These relevant facts, whose actual origin is discussed in Refs.…”

Section: Non-degenerate Two-site Polaron Modelmentioning

confidence: 99%

Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides: Insight through DFT+UCalculations

et al. 2016

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Polarons and their associated transport properties are a field of great current interest both in chemistry and physics. In order to further our understanding of these quasi-particles, we have carried out first-principles calculations of self-trapped holes (STH) in the model compounds AgCl and AgBr, where extensive experimental information exists. Our calculations confirm that the STH solely stabilizes in AgCl but with a binding energy of only 165 meV, an order of magnitude smaller than that found for the Vk center in KCl. Key contributions to this stabilization energy come from the local relaxation along breathing (a1g) and Jahn-Teller (eg) modes in the AgCl6 4-unit. In order to study the transfer of the STH among silver sites we (i) use first-principles calculations to obtain the hopping barrier of the STH to first and second neighbors, involving eight distinct paths, using firstprinciples and (ii) construct a simple model, based on Slater-Koster parameters, that highlights the similarity of polaron transfer with magnetic superexchange. This allows one understanding why the movement of STH to second neighbors is highly enhanced with respect to closer ones. In agreement with experimental data and the model, the present calculations prove the existence of a dominant mechanism of polaronic motion that corresponds to the displacement of the STH to the next nearest sites in the <100> direction and a small barrier of 37 meV. This mechanism is dominated by the covalency inside a AgX6 4-complex (X:Cl;Br) thus explaining why the STH is not stabilized in AgBr following the increase of covalency due to the ClBr substitution. The present calculations confirm that ~10% of the charge associated with the STH in AgCl is lying outside the AgCl6 4-complex. This fact is behind the differences between optical and magnetic properties of the STH in AgCl and those observed in KCl:Ag 2+ .2

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New Ideas for Understanding the Structure and Magnetism in AgF₂: Prediction of Ferroelasticity

Sánchez-Movellán

García‐Fernández

Aramburu

et al. 2021

Chemistry A European J

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In the search for new high‐temperature superconductors, it has been proposed that there are strong similarities between the fluoroargentate AgF2 and the cuprate La2CuO4. We explored the origin of the possible layered structure of AgF2 by studying its parent high‐symmetry phase and comparing these results with those of a seemingly analogous cuprate, CuF2. Our findings first stress the large differences between CuF2 and AgF2. Indeed, the parent structure of AgF2 is found to be cubic, naturally devoid of any layering, even though Ag2+ ions occupy trigonal sites that, nevertheless, allow the existence of a Jahn‐Teller effect. The observed Pbca orthorhombic phase is found when the system is cooperatively distorted by a local E⊗e trigonal Jahn‐Teller effect around the silver sites that creates both geometrical and magnetic layering. While the distortion implies that two Ag2+−F− bonds increase their distance by 15 % and become softer, our simulations indicate that covalent bonding and interlayer electron hopping is strong, unlike the situation in cuprate superconductors, and that, in fact, exfoliation of individual planes might be a harder task than previously suggested. As a salient feature, these results prove that the actual magnetic structure in AgF2 is a direct consequence of vibronic contributions involved in the Jahn‐Teller effect. Finally, our findings show that, due to the multiple minima intrinsic to the Jahn‐Teller energy surface, the system is ferroelastic, a property that is strongly coupled to magnetism in this argentate.

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Jahn–Teller effect in Ag2+ doped KCl and NaCl: Is there any influence of the host lattice?

Cited by 23 publications

References 14 publications

Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides: Insight through DFT+UCalculations

New Ideas for Understanding the Structure and Magnetism in AgF₂: Prediction of Ferroelasticity

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Jahn–Teller effect in Ag2+ doped KCl and NaCl: Is there any influence of the host lattice?

Cited by 23 publications

References 14 publications

Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni+

Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni+

Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides: Insight through DFT+UCalculations

New Ideas for Understanding the Structure and Magnetism in AgF2: Prediction of Ferroelasticity

Contact Info

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Resources

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Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

Origin of Small Barriers in Jahn–Teller Systems: Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni⁺

New Ideas for Understanding the Structure and Magnetism in AgF₂: Prediction of Ferroelasticity