title: Correlation between local vibrations and metal mass in AlB2-type transition-metal diborides.
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.
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: W S
authors.initials: WS
authors.lastname: Chu
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: M J
authors.initials: MJ
authors.lastname: Yu
authors.forename: L R
authors.initials: LR
authors.lastname: Zheng
authors.forename: T D
authors.initials: TD
authors.lastname: Hu
authors.forename: H F
authors.initials: HF
authors.lastname: Zhao
authors.forename: A
authors.initials: A
authors.lastname: Marcelli
authors.forename: A
authors.initials: A
authors.lastname: Bianconi
authors.forename: N L
authors.initials: NL
authors.lastname: Saini
authors.forename: W H
authors.initials: WH
authors.lastname: Liu
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Wu