Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems
Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH/sub 2/ and YH/sub 2/ were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are then used to simulate the derivative structure in thermomodulation spectra and relate the origin of experimental interband features to the calculated energy bands. While good systematic agreement is obtained for several spectral features, the origin of low-energy interband transitions in YH/sub 2/ cannot be explained by these calculated bands. A lattice-size-dependent premature occupation of octahedral sites by hydrogen atoms in the fcc metal lattice is suggested to account for this discrepancy. Various non-self-consistent calculations are used to examine the effect of such a premature occupation. Measurements of the optical absorptivity of LaH/sub x/ with 1.6 < x < 2.9 are presented which, as expected, indicate a more premature occupation of the octahedral sites in the larger LaH/sub 2/ lattice. These experimental results also suggest that, in contrast to recent calculations, LaH/sub 3/ is a small-band-gap semiconductor.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5068113
- Report Number(s):
- IS-T-899; TRN: 80-015356
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
08 HYDROGEN
HYDROGEN STORAGE
LANTHANUM HYDRIDES
OPTICAL PROPERTIES
SCANDIUM HYDRIDES
YTTRIUM HYDRIDES
BAND THEORY
ELECTRONIC STRUCTURE
HYDROGEN EMBRITTLEMENT
MATHEMATICAL MODELS
EMBRITTLEMENT
HYDRIDES
HYDROGEN COMPOUNDS
LANTHANUM COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SCANDIUM COMPOUNDS
STORAGE
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360104* - Metals & Alloys- Physical Properties
080201 - Hydrogen- Chemisorption Storage