We present a general theoretical scheme that allows an accurate account of the vibrational broadening of core-level line shapes in crystals, using state-of-the-art electronic-structure techniques within the Franck-Condon approximation. Electronic and vibrational degrees of freedom are consistently treated using ab initio density-functional theory. Neglecting the core-hole lifetime, anharmonic effects are treated within a self-consistent phonon approach. Finite core-hole lifetime effects are simulated by an independent-boson model, which, however, we have been able to apply only when lattice distortions are treated in the harmonic approximation. We apply the theory to the diamond Is core-level emission spectrum. In the limit of infinite core-hole lifetime, we find that (i) the Stokes shift is about 3 eV, (ii) the harmonic approximation overestimates the Stokes shift by similar to 1.4 eV, and (iii) phonon broadening is about 2 eV. A comparison with experiment reveals that the phonon bandwidth is comparable to the core-hole lifetime, which we estimate Gamma approximate to 110 meV.

Vibrational broadening of x-ray emission spectra: A first-principles study on diamond / Mader, K. A.; Baroni, S.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER. - ISSN 0163-1829. - 55:15(1997), pp. 9649-9658. [10.1103/PhysRevB.55.9649]

Vibrational broadening of x-ray emission spectra: A first-principles study on diamond

Baroni, S.
1997-01-01

Abstract

We present a general theoretical scheme that allows an accurate account of the vibrational broadening of core-level line shapes in crystals, using state-of-the-art electronic-structure techniques within the Franck-Condon approximation. Electronic and vibrational degrees of freedom are consistently treated using ab initio density-functional theory. Neglecting the core-hole lifetime, anharmonic effects are treated within a self-consistent phonon approach. Finite core-hole lifetime effects are simulated by an independent-boson model, which, however, we have been able to apply only when lattice distortions are treated in the harmonic approximation. We apply the theory to the diamond Is core-level emission spectrum. In the limit of infinite core-hole lifetime, we find that (i) the Stokes shift is about 3 eV, (ii) the harmonic approximation overestimates the Stokes shift by similar to 1.4 eV, and (iii) phonon broadening is about 2 eV. A comparison with experiment reveals that the phonon bandwidth is comparable to the core-hole lifetime, which we estimate Gamma approximate to 110 meV.
1997
55
15
9649
9658
Mader, K. A.; Baroni, S.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/15941
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