Electronic properties and electron-phonon coupling in zirconium and niobium hydrides

Journal Article · Fri Jan 15 00:00:00 EST 1982 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.25.1027· OSTI ID:5591530

Gupta, M

The electronic structure of the two 4d transition-metal cubic dihydrides ZrH/sub 2/ and NbH/sub 2/ is investigated by means of an augmented-plane-wave (APW) band-structure calculation. The position of the Fermi level in a peak of the density of states (DOS) in the case of cubic ZrH/sub 2/ leads to an interpretation of the tetragonal distortion observed in all the group-IV transition-metal dihydrides in terms of a Jahn-Teller effect which lifts the degeneracy of the doubly degenerate band in the GAMMAL direction; these results are in agreement with magnetic susceptibility, electronic specific heat and thermoelectric power data. The main features of the DOS of the metal 4d states are similar for ZrH/sub 2/ and NbH/sub 2/, while the position and width of the low-lying bands are found to depend substantially upon the compound under study. These two bands which result from metal-hydrogen and hydrogen-hydrogen interactions overlap the metal d bands located at higher energies, contrary to the case of rare-earth dihydrides for which an energy gap was obtained. Our theoretical results are in good agreement with photoemission and x-ray emission spectra. We have evaluated the electron-phonon coupling constant lambda using the results of our APW calculation in conjunction with neutron scattering data. For both ZrH/sub 2/ and NbH/sub 2/, and contrary to the case of superconducting PdH, the electron-optical phonon contribution is small, due essentially to the low value of the DOS of s type at the H site at the Fermi energy and to the hardening of the optic modes. Moreover, the electronic term of the electron--acoustic-phonon contribution is reduced from its value in the pure metal. The two compounds are not found to be superconducting, in agreement with experimental results.

• Research Organization: Centre de Mecanique Ondulatoire Appliquee du Centre National de la Recherche, 23 rue du Maroc, 75019 Paris, France
• OSTI ID: 5591530
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Vol. 25:2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
NIOBIUM HYDRIDES
ELECTRONIC STRUCTURE
SUPERCONDUCTIVITY
ZIRCONIUM HYDRIDES
BAND THEORY
COUPLING CONSTANTS
ELECTRON-PHONON COUPLING
ENERGY GAP
FERMI LEVEL
PHOTOELECTRON SPECTROSCOPY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON SPECTROSCOPY
ENERGY LEVELS
HYDRIDES
HYDROGEN COMPOUNDS
NIOBIUM COMPOUNDS
PHYSICAL PROPERTIES
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)