Total-energy study of hydrogen ordering in PdH{sub {ital x}} (0{le}{ital x}{le}1)

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.1· OSTI ID:253510

Wang, Y; Sun, S N; Chou, M Y ^[1]

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1. School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)

We studied total energies of various ordered structures of PdH{sub {ital x}} (in which hydrogen occupies the octahedral sites within the fcc Pd lattice) using the pseudopotential method and a plane-wave basis within the local-density-functional approximation. The structures considered include the (420)-plane ordering of hydrogen atoms at different concentrations. For {ital x}{ge}1/2 we found that the NiMo- and Ni{sub 4}Mo ({ital D}1{sub {ital a}})-type structures at {ital x}=1/2 and {ital x}=4/5, respectively, were energetically favored phases, in agreement with the superlattice reflections found in previous neutron-scattering measurements. For the intermediate concentrations, linear variation of the formation energy as a function of {ital x} in several (420)-ordered structures explained the observed short-range order. In contrast to an earlier proposal, we did not find the Fermi surface imaging effect responsible in this case. The overall energy variation in different phases indicates the importance of going beyond pairwise interactions between interstitial hydrogen atoms in this system. {copyright} {ital 1996 The American Physical Society.}

• DOE Contract Number: FG05-90ER45431
• OSTI ID: 253510
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 1 Vol. 53; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
DENSITY FUNCTIONAL METHOD
ELECTRONIC STRUCTURE
FCC LATTICES
HYDROGEN
INTERSTITIALS
NEUTRON DIFFRACTION
ORDERED SYSTEMS
PALLADIUM HYDRIDES
PHASE STUDIES
PSEUDOPOTENTIAL
STRUCTURAL MODELS