Properties of F+, F and F− electron centers and adsorptivity of atomic H on LiF and NaH isoelectronic crystals: an ab initio study

Shalabi, A.S.; Mahdy, A.M. El; Kamel, M.A.; Ammar, H.Y.

doi:10.1016/s0921-4526(01)00393-3

Cited by 15 publications

(2 citation statements)

References 24 publications

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“…For the excited state, the same procedure was applied within one of the B u symmetries. For the medium cluster and medium basis set, the largest CASs tested were (19,13) corresponding to 19 electrons in 13 orbitals and (17,11) for the ground and excited state, respectively, leading to only small shifts of the total energies. This indicates the strong dominance of a single configuration.…”

Section: Quantum-chemistry Methods and Cluster Sizementioning

confidence: 99%

“…These calculations are either based on densityfunctional theory (DFT) [15,16] treating the extended system using periodic boundary conditions, or on quantum-chemical methods [16][17][18][19] explicitly treating a cluster. Previous DFT calculations were based on the local-density approximation (LDA) suffering from the well known underestimate of the band gap for insulators [20][21][22] and the unphysical delocalization of localized states.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

Karsai¹,

Tiwald²,

Laskowski³

et al. 2014

Phys. Rev. B

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We revisit the theoretical description of the F color center in lithium fluoride employing advanced complementary ab initio techniques. We compare the results from periodic supercell calculations involving density-functional theory (DFT) and post-DFT techniques with those from the embedded-cluster approach involving quantumchemical many-electron wave-function techniques. These alternative approaches yield results in good agreement with each other and with the experimental data provided that correlation effects are properly taken into account.

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Section: Quantum-chemistry Methods and Cluster Sizementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

Karsai¹,

Tiwald²,

Laskowski³

et al. 2014

Phys. Rev. B

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F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

Shalabi

2002

J Comput Chem

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The twofold potentials of F(A)(I):Au(+) and F(A)(II)Cu(+) color centers at the low coordinated surfaces of AgBr thin films in providing tunable laser activity and photographic sensitization were investigated using ab initio methods of molecular electronic structure calculations. Clusters of variable size were embedded in simulated Coulomb fields that closely approximated the Madelung fields of the host surfaces, and the nearest neighbor ions to the F(A) defect site were allowed to relax to equilibrium in each case. Based on the calculated Stokes shifted optical transition bands and horizontal shifts along the configuration coordinate diagrams, both F(A)(I):Au(+) and F(A)(II):Cu(+) color centers were found to be laser active. The laser activity faded quickly as the bromide ion coordination decreased from 5 (flat) to 4 (edge) to 3 (corner) and as the size of the impurity cation increased from Cu(+) to Au(+). The latter relation was explainable in terms of the axial perturbation of the impurity cation. The smallest calculated Stokes-shift at the corner surface suggested that emission had the same oscillator strength as absorption. All relaxed excited states RESs of the defect containing surfaces were deep below the lower edges of the conduction bands of the defect free ground state surfaces, indicating that F(A)(I):Au(+) and F(A)(II):Cu(+) are suitable laser defects. The probability of orientational destruction of the two centers attributed to the assumed RES saddle point ion configurations along the <110> axis was found to be directly proportional to the size of the impurity cation, with activation energy barriers of about 0.655-3.294 eV for Cu(+), and about 1.887-3.404 eV for Au(+). The possibility of exciton (energy) transfer from the sites of higher coordination to those of lower coordination is demonstrated. The more laser active F(A)(II):Cu(+) center was more easily formed than the less laser active F(A)(I):Au(+) center. The Glasner-Tompkins empirical relation was generalized to include F(A) centers at the low coordinated surfaces of silver bromide thin film. As far as color photographic sensitization is concerned, the lowest unoccupied molecular orbitals of the selected dye molecules in the excited states were high enough for electron injection. F(A) defect formation and rotational diffusion of silver clusters reduced the energy gaps between the excited dye molecules and the lower edges of the conduction bands and allowed for hole injection. About 54-60% of the reduction of silver ions at the flat surface of AgBr was attributed to the host anions and F(A) defect formation, leaving about 40-46% for the reduction of photoelectrons as well as the electrons of the developer or dye molecules. The unrelaxed rotational diffusions of the central Ag(4) by 90 degrees decreased the latter percentage, but were severely hindered by activation energy barriers.

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Theoretical study of laser light generation and color image formation:F_A1:Cs⁺andF_A2:Li⁺centers at the low coordination (100) and (110) surfaces of AgCl and AgBr

Shalabi

Kamel

Ammar

2005

Int J of Quantum Chemistry

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ABSTRACT:The F A1 :Cs ϩ and F A2 :Li ϩ color centers at the low coordination (100) and (110) surfaces of AgCl and AgBr play important roles in laser light generation and color image formation. Double-well potentials at these surfaces are investigated by using ab initio calculations. Quantum clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces, and ions that are the nearest neighbors to the F A Ϫ defect site are allowed to relax to equilibrium. The calculated Stokes shifts suggest that laser light generation is sensitive to the simultaneous effects of the vibrational coupling mode, the impurity cation, the coordination number of the surface ion, the lattice anion, and the choice of the basis set centered on the anion vacancy. An attempt has been made to explain these effects in terms of Madelung potential, electron affinity, and optical-optical conversion efficiency. All relaxed excited states of the defect-containing surfaces are deep below the lower edges of the conduction bands of the ground-state defect-free surfaces, suggesting that the F A (I):Cs ϩ and F A (II):Li ϩ centers are suitable laser defects. The dependence of orientational destruction, recording sensitivity, and exciton (energy) transfer on the empty cation; the coordination number of the surface ion; and the lattice anion is clarified. The Glasner-Tompkins empirical rule was generalized to include the impurity cation and the coordination number of the surface ion. As far as color image formation is concerned, the supersensitizer was found to increase the sensitizing capabilities of two primary dyes in the excited states by increasing the relative yield of quantum efficiency. The (110) surfaces of AgBr and AgCl were more sensitive than the corresponding (100) surfaces, and AgBr thin film was found to be more sensitive than that of AgCl. On the basis of quasi-Fermi levels, the difference in the sensitizing capabilities between the examined dyes in the excited states is determined.

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Properties of F+, F and F− electron centers and adsorptivity of atomic H on LiF and NaH isoelectronic crystals: an ab initio study

Cited by 15 publications

References 24 publications

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

Theoretical study of laser light generation and color image formation:F_A1:Cs⁺andF_A2:Li⁺centers at the low coordination (100) and (110) surfaces of AgCl and AgBr

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Properties of F+, F and F− electron centers and adsorptivity of atomic H on LiF and NaH isoelectronic crystals: an ab initio study

Cited by 15 publications

References 24 publications

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

FA(I):Au+andFA(II):Cu+laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

Theoretical study of laser light generation and color image formation:FA1:Cs+andFA2:Li+centers at the low coordination (100) and (110) surfaces of AgCl and AgBr

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F_A(I):Au⁺andF_A(II):Cu⁺laser activity and photographic sensitization at the low coordinated surfaces of AgBrab initiocalculations

Theoretical study of laser light generation and color image formation:F_A1:Cs⁺andF_A2:Li⁺centers at the low coordination (100) and (110) surfaces of AgCl and AgBr