Hole self trapping and recombination luminescence in AgCl at low temperatures

Marquardt, C. L.; Williams, Richard; Kabler, M. N.

doi:10.1016/0038-1098(71)90650-8

Cited by 61 publications

(22 citation statements)

References 9 publications

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“…These results thus support that STHs can be spontaneously produced in irradiated AgCl. Moreover, they are consistent with experimental EPR and ENDOR data on this compound proving the formation of elongated AgCl6 4-complexes with the hole placed in the antibonding x 2 -y 2 orbital 19,23,25,27,35 .…”

Section: Stability Of Self-trapped Holes In Agclsupporting

confidence: 88%

“…As the energy of such a transition, denoted as E(z 2 ), would be zero if the 23 octahedral AgCl6 4-complex is placed in a cubic lattice 90 it depends on the tetragonal distortion in the complex reflected in the Rax -Req = 3 quantity. As in a JT system E(z 2 )  4EJT 41 This luminescence is well observed in AgCl crystals doped with copper and grown in a chlorine atmosphere where self-trapped holes and electrons trapped as Cu + are both simultaneously formed 21,27 .…”

Section: Optical Properties Of the Self-trapped Hole In Agclmentioning

confidence: 71%

“…This expression, using m* = 0.215m and L = 3.66 10 13 rad, leads to an extension of the large polaron around 30 Å for AgCl 98 which is thus an order of magnitude higher than that for the STH. 27 Although electrons placed in the conduction band of alkali and silver halides are not self- Table 2. Slater-Koster parameters 52 for expressing the inter-site parameters, , for the cases shown in Fig. 2b.…”

Section: Final Remarksmentioning

confidence: 99%

“…Despite this, the hyperfine and the isotropic superhyperfine constants measured for the STH in AgCl are somewhat smaller than those for KCl:Ag 2+ or NaCl:Ag 2+ 38 (Table 1) thus suggesting that a fraction of the unpaired electron in AgCl is lying outside the AgCl6 4- Moreover, that study showed the existence of a dominant mechanism of polaronic hopping, involving an activation energy of 61  3 meV 25 , whose nature is hitherto unknown. As regards the 5 optical absorption transitions associated with the STH in AgCl, there is a band peaked at 1.2 eV measured experimentally whose origin has not been clarified yet 21,27,31 . Interestingly, when shinning the AgCl sample with this infrared light the concentration of STH decreases 21 , a phenomenon that still needs to be understood.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Stability Of Self-trapped Holes In Agclsupporting

confidence: 88%

Section: Optical Properties Of the Self-trapped Hole In Agclmentioning

confidence: 71%

Section: Final Remarksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…[13][14][15] The quenching spectrum of the heat generation in Fig. 11 is similar to the absorption spectra of the self-trapped holes or deeply trapped holes.…”

Section: Discussionmentioning

confidence: 58%

Photoinduced anomalous heat generation in AgCl and AgBr single crystals at liquid-helium temperature

1997

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Anomalous heat generation induced by band-gap light illumination was observed in AgCl and AgBr single crystals by a sensitive photocalorimetric method at liquid-helium temperature. The generated heat per second was estimated to be one to two orders of magnitude larger than the absorbed energy per second. This heat generation lasted for more than 10 h after termination of the band-gap light illumination, indicating that exothermic chain reactions were triggered by the absorbed photons. In a crystal which was not annealed, total emitted heat energy was estimated to be as high as 0.17 eV per unit cell. Consecutive nonradiative recombination of interstitial silver ions and vacancies mediated by the photoelectrons are tentatively proposed to be the responsible chain reactions. Although most of the features of the heat generation can be explained by the proposed mechanism, this mechanism requires an unrealistically high concentration of interstitial-vacancy pairs to explain the total emitted energy, leaving the observed anomalous phenomenon unexplained.

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The Photochemistry and Photophysics of the Silver Halides

Marchetti

Eachus

1992

Advances in Photochemistry

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Hole self trapping and recombination luminescence in AgCl at low temperatures

Cited by 61 publications

References 9 publications

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

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

Photoinduced anomalous heat generation in AgCl and AgBr single crystals at liquid-helium temperature

The Photochemistry and Photophysics of the Silver Halides

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