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Ab initio calculations of the forbidden Bragg reflections energy spectra in wurtzites versus temperature

DOI: 10.1088/0953-8984/24/24/245403 DOI Help

Authors: A. P. Oreshko (Moscow State University, Russia) , E. N. Ovchinnikova (Moscow State University) , G. Beutier (CEA, INAC) , S. P. Collins (Diamond Light Source) , G. Nisbet (Diamond Light Source) , A. M. Kolchinskaya (Technische Universitat Darmstadt, Germany) , V. E. Dmitrienko (AV Shubnikov Institute of Crystallography)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Physics: Condensed Matter , VOL 24 (24)

State: Published (Approved)
Published: June 2012

Abstract: Thermal-motion induced (TMI) scattering is caused by the influence of atomic displacements on electronic states in crystals and strongly depends on temperature. It corresponds to dipole–dipole resonant x-ray scattering, but is usually accompanied by dipole–quadrupole scattering. The phenomenological theory supposes the dipole–quadrupole term to be temperature independent (TI). As a result, the transformation of the energy spectra with temperature observed experimentally in ZnO and GaN corresponds to the interference between the TMI and TI terms. In the present paper the direct confirmation of this theoretical prediction is given. Ab initio molecular dynamics was used to simulate the sets of atomic sites at various temperatures followed by quantum mechanical calculation of resonant Bragg reflection energy spectra. The results of simulation are in excellent coincidence with experimental energy spectra of forbidden reflections and confirm the earlier phenomenological conjecture about the interference between the TI dipole–quadrupole and TMI dipole–dipole contributions to the resonant atomic factor.

Journal Keywords: Atomic Displacements; Bragg Reflection; Crystals; Dipoles; Energy Spectra; Gallium Nitrides; Molecular Dynamics Method; Quantum Mechanics; Resonance; Simulation; Temperature Dependence; X-Ray Diffraction; Zinc Oxides

Subject Areas: Physics, Materials

Instruments: I16-Materials and Magnetism

Other Facilities: Yes ESRF

Added On: 29/09/2012 12:50

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