Study of temperature dependent atomic correlations in MgB${}_2$

Abstract

We have studied the evolution with temperature of the local as well as the average crystal structure of MgB${}_2$ using the real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction. We have investigated the correlations of the B-B and B-Mg nearest neighbor pair motion by comparing, in the wide temperature range from T=10 K up to T=600 K, the mean-square displacements (MSD) of single atoms with the mean-square relative displacements (MSRD) obtained from the PDF peak linewidths. The results show that the single atom B and Mg vibrations are mostly decoupled from each other, with a small predominance of positive (in phase) correlation factor for both the B-B and B-Mg pairs. The small positive correlation is almost temperature independent, in contrast with our theoretical calculations; this can be a direct consequence of the strong decay processes of the $E_{2g}$ anharmonic phonons.

References in corpus (1)

• Definitive experimental evidence for two-band superconductivity in MgB2

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