Lattice vibrations have been investigated in TiB2, ZrB2 and HfB2 by temperature-dependent extended X-ray absorption fine structure (EXAFS) experiments. Data clearly show that the EXAFS oscillations are characterized by an anomalous behavior of the Debye-Waller factor of the transition-metal-boron pair, which is suggested to be associated with a superposition of an optical mode corresponding to phonon vibrations induced by the B sublattice and an acoustic mode corresponding to the transition-metal (TM) sublattice. Data can be interpreted as a decoupling of the metal and boron vibrations observed in these transition-metal diborides (TMB2), a mechanism that may be responsible for the significant reduction of the superconducting transition temperature observed in these systems with respect to the parent MgB2 compound. The vibrational behavior of TM-TM bonds has also been investigated to study the occurrence of anisotropy and anomalies in the lattice vibrational behavior of TM-TM bonds.
Correlation between local vibrations and metal mass in AlB2-type transition-metal diborides / W. S., C., S., Z., M. J., Y.u., L. R., Z., T. D., H.u., H. F., Z., A., M., Bianconi, A., Saini, N.L., W. H. LIU, Z.Y.W.. - In: JOURNAL OF SYNCHROTRON RADIATION. - ISSN 0909-0495. - 16:(2009), pp. 30-37. [10.1107/S0909049508030628]
Correlation between local vibrations and metal mass in AlB2-type transition-metal diborides
BIANCONI, Antonio;SAINI, Naurang Lal;
2009
Abstract
Lattice vibrations have been investigated in TiB2, ZrB2 and HfB2 by temperature-dependent extended X-ray absorption fine structure (EXAFS) experiments. Data clearly show that the EXAFS oscillations are characterized by an anomalous behavior of the Debye-Waller factor of the transition-metal-boron pair, which is suggested to be associated with a superposition of an optical mode corresponding to phonon vibrations induced by the B sublattice and an acoustic mode corresponding to the transition-metal (TM) sublattice. Data can be interpreted as a decoupling of the metal and boron vibrations observed in these transition-metal diborides (TMB2), a mechanism that may be responsible for the significant reduction of the superconducting transition temperature observed in these systems with respect to the parent MgB2 compound. The vibrational behavior of TM-TM bonds has also been investigated to study the occurrence of anisotropy and anomalies in the lattice vibrational behavior of TM-TM bonds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
