We have studied temperature evolution of the local as well as the average crystal structure of MgB2 and Mg0.5Al0.5B2 using real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction in a wide temperature range of T=10600 K. The mean square relative displacements (MSRD) of atomic BB, BMg (BAl) pairs are compared with mean-square displacements (MSD) to calculate atomic correlations. In spite of the enhanced atomic disorder in Mg0.5Al0.5B2, where the boronboron, and boronmagnesium pair motions are found to be small, we find that the same atomic correlations in MgB2 assume even slightly lower values and remain nearly constant in a wide temperature range of 0600 K. This anomalous behavior and its physical interpretation provoke new questions on our understanding to the local lattice dynamics in this material.
Local Lattice Dynamics in the Mg0.5Al0.5B2 Superconductor
Campi G;
2007
Abstract
We have studied temperature evolution of the local as well as the average crystal structure of MgB2 and Mg0.5Al0.5B2 using real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction in a wide temperature range of T=10600 K. The mean square relative displacements (MSRD) of atomic BB, BMg (BAl) pairs are compared with mean-square displacements (MSD) to calculate atomic correlations. In spite of the enhanced atomic disorder in Mg0.5Al0.5B2, where the boronboron, and boronmagnesium pair motions are found to be small, we find that the same atomic correlations in MgB2 assume even slightly lower values and remain nearly constant in a wide temperature range of 0600 K. This anomalous behavior and its physical interpretation provoke new questions on our understanding to the local lattice dynamics in this material.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
