Energy Generation: Solar Energy

Botti, Silvana; Vidal, Julien

doi:10.1002/9781118551462.ch2

Cited by 2 publications

(2 citation statements)

References 161 publications

(274 reference statements)

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“…Working inside of first-principles electronic structure methods, a useful way of making such treatment is consideration of the non-local hybrid functional as an approximation to the true electron selfenergy Σ(x, x ′ ; ω) , which provides theoretical constructs that map efficiently to typical elements of the hybrid functional like as follows: 39,40 Σ(x, x ′ ; ω) is projected into the direct sum of two principal terms -the first corresponds to a statically screened non-local exchange in which the amount of the exchange is driven by the inverse electronic dielectric constant ǫ −1 ∞ and the second is identified with the static and local part of the hybrid functional; the quasi-particle equation followed from such construction corresponds to the generalized Kohn-Sham equation that can be self-consistently solved for a hybrid functional. The main benefit that was originally gained in this context is that by including the fraction a (the mixing coefficient) of the Fock exchange as ǫ…”

Section: Methods and Computational Details A Methodological Aspectsmentioning

confidence: 99%

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Pishtshev

Karazhanov

Klopov

2014

Computational Materials Science

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This work presents a study of ground state properties, electronic structure, dielectric and optical properties of magnesium and calcium hydroxides X(OH)2 (X = Mg and Ca) within PBE-GGA and range-separated hybrid functional schemes as well as by using GW approximation. The relevant HSE06 hybrid functional mixing parameters were determined from a self-consistent adjustment to the electronic dielectric constant ǫ∞. It was shown that the overall performance of our adaptation of the HSE06 functional via implementation of the modified amount of the Fock exchange is nearly best for the ground state properties as compared to other relevant HF and DFT methods. Structural stability of the crystalline X(OH)2 hydroxides has been considered in static and dynamic aspects. The most important factors describing the bonding situation have been investigated, and a crystalchemical integrity of the hydroxides has been analyzed. From electronic structure studies it was found that both materials are direct band gap insulators. Predictions for the fundamental band gaps were shown to be in the range of 7.7-8.3 eV for Mg(OH) 2 and 7.3-7.6 eV for Ca(OH) 2 . The origin of the conduction and valence band states near the band edges has been studied in terms of orbital and site projected density of states as well as by comparison with the X-ray photoelectron spectroscopy measurements. It was shown that effective masses of carriers at the Γ-point in vicinity of the band extreme are strongly anisotropic and for the electrons are similar to those in the ZnO crystal. Optical properties of the bulk X(OH)2 hydroxides have been investigated in terms of the real and imaginary parts of the optical dielectric function calculated in GW approximation. Electronic character of anisotropy of optical properties has been clarified. On the base of the obtained results the potential of applicability of the Mg(OH) 2 and Ca(OH) 2 crystalline hydroxides in semiconductor device engineering and optoelectronics has been analyzed.

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Section: Methods and Computational Details A Methodological Aspectsmentioning

confidence: 99%

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Pishtshev

Karazhanov

Klopov

2014

Computational Materials Science

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“…For description of exchange effects in a periodic ion-covalent insulating system we employ the relation a≈ǫ −1 ∞ (Ref. [30][31][32][33][34]) that approximates the mixing coefficient a (fraction of the Fock exchange) in the xc potential in terms of the effective screening of the bare nonlocal exchange part of the electron-electron interaction [31,35].…”

Section: Structural Model and Computational Detailsmentioning

confidence: 99%

Excitons in Mg(OH)2 and Ca(OH)2 from ab initio calculations

Pishtshev

Karazhanov

Klopov

2014

Solid State Communications

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By using ab initio calculations with the HSE06 hybrid functional and GW approximation combined with numerical solution of the Bethe Salpeter equation (GW-BSE) we predict the existence of diverse number of excitonic states in multifunctional hydroxides X(OH)2 (X = Mg and Ca) that were not previously reported experimentally or theoretically. Imaginary part of the dielectric function and reflectivity spectra show very strong peaks corresponding to the electron-hole pair states of large binding energy. The origin of the excitons is attributed to strong localization of the hole and electron associated to oxygen 2p x , 2p y occupied states as well as to oxygen and earth metal s empty states, respectively. The results have important implications for different applications of the materials in optoelectronic devices.

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Energy Generation: Solar Energy

Cited by 2 publications

References 161 publications

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Excitons in Mg(OH)2 and Ca(OH)2 from ab initio calculations

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