Pseudopotential plane-wave study of [alpha]-YH[sub [ital x]]

Journal Article · Sun May 15 04:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.13357· OSTI ID:7284072

Wang, Y; Chou, M Y ^[1]

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1. School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

The solid-solution phase of hydrogen in hexagonal close-packed yttrium ([alpha]-YH[sub [ital x]]) is studied using the pseudopotential method within the local-density-functional approximation with a plane-wave basis. The binding energies associated with different interstitial sites are evaluated for several ordered structures: YH[sub 0.5], YH[sub 0.25], and YH[sub 0.167]. It is found that the occupation of the tetrahedral site is always energetically favorable. The hydrogen potential-energy curves around the tetrahedral sites along the [ital c] axis and along the path connecting the adjacent octahedral sites are also calculated for YH[sub 0.25]. In particular, the local vibrational mode along the [ital c] axis is estimated to be 100 meV, in excellent agreement with that measured in neutron-scattering experiments. Finally, the intriguing pairing phenomenon is investigated by calculating the total energy for various pairing configurations. The possibility of pairing between nearest-neighbor tetrahedral sites is excluded due to the high energy. It is found that the pairing of hydrogen across a metal atom is indeed energetically favorable compared with other kinds of pairs considered and also with isolated tetrahedral hydrogen atoms. The connection with the electronic structure of the system is also examined.

• DOE Contract Number: FG05-90ER45431
• OSTI ID: 7284072
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 49:19; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
BINDING ENERGY
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DISPERSIONS
ELECTRONIC STRUCTURE
ENERGY
ENERGY LEVELS
EXCITED STATES
HCP LATTICES
HEXAGONAL LATTICES
HYDRIDES
HYDROGEN COMPOUNDS
INTERACTIONS
INTERSTITIALS
MIXTURES
PAIRING INTERACTIONS
POINT DEFECTS
POTENTIAL ENERGY
SOLID SOLUTIONS
SOLUTIONS
TRANSITION ELEMENT COMPOUNDS
VIBRATIONAL STATES
YTTRIUM COMPOUNDS
YTTRIUM HYDRIDES