Numerical simulation of the forbidden Bragg reflection spectra observed in ZnO

• Published in: Journal of physics. Condensed matter Vol. 22; no. 35; p. 355404
• Main Authors: Ovchinnikova, E N, Dmitrienko, V E, Oreshko, A P, Beutier, G, Collins, S P
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 08.09.2010; IOP Publishing [1989-....]
• Subjects: Condensed Matter; Physics; Strongly Correlated Electrons
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/35/355404

Thermal motion induced (TMI) scattering is a unique probe of changes in electronic states with atomic displacements in crystals. We show that it provides a novel approach to extract atomic correlation functions. Using numerical calculations, we are able to reproduce the temperature-dependent energy spectrum of the 115 'forbidden' Bragg reflection in ZnO. Our previous experimental studies showed that the intensity growth of such reflections over a wide range of temperatures is accompanied by a dramatic change in the resonant spectral lineshape. This is the result of the interplay between the temperature-independent (TI) and temperature-dependent TMI contributions. Here, we confirm that the TI part of the resonant structure factor can be associated with the dipole-quadrupole contribution to the structure factor and show that the temperature-dependent part arises from the zinc and oxygen vibrations, which provide additional temperature-dependent dipole-dipole tensor components to the structure factor. By fitting the experimental data at various temperatures we have determined the temperature dependences of autocorrelation <u(x)(2)(Zn)> and correlation <u(x)(O)u(x)(Zn)> functions.