WH[eta] under pressure
- Cornell
An initial observation of the formation of WH under pressure from W gaskets surrounding hydrogen in diamond anvil cells led to a theoretical study of tungsten hydride phases. At P = 1 atm no stoichiometry is found to be stable with respect to separation into the elements, but as the pressure is raised WH{sub n} (n = 1-6, 8) stoichiometries are metastable or stable. WH and WH{sub 4} are calculated to be stable at P > 15 GPa, WH{sub 2} becomes stable at P > 100 GPa and WH{sub 6} at P > 150 GPa. In agreement with experiment, the structure computed for WH is anti-NiAs. WH{sub 2} shares with WH a hexagonal arrangement of tungsten atoms, with hydrogen atoms occupying octahedral and tetrahedral holes. For WH{sub 4} the W atoms are in a distorted fcc arrangement. As the number of hydrogens rises, the coordination of W by H increases correspondingly, leading to a twelve-coordinated W in WH{sub 6}. In WH{sub 8} H{sub 2} units also develop. All of the hydrides considered should be metallic at high pressure, though the Fermi levels of WH{sub 4} and WH{sub 6} lie in a deep pseudogap. Prodded by these theoretical studies, experiments were then undertaken to seek phases other than WH, exploring a variety of experimental conditions that would favor further reaction. Though a better preparation and characterization of WH resulted, no higher hydrides have as yet been found.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- NSFDOE - BASIC ENERGY SCIENCES
- OSTI ID:
- 1037912
- Journal Information:
- J. Phys. Condens. Matter, Vol. 24, Issue (15) ; 03, 2012; ISSN 0953-8984
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Tungsten(VI) hexahydride complexes supported by chelating triphosphine ligands: Protonation to give [eta][sup 2]-dihydrogen complexes and catalytic dehydrogenation of cyclooctane to cyclooctene
Molybdenum and tungsten complexes of S[sub 2]CPMe[sub 3] and related ligands. Crystal and molecular structures of W([eta][sup 3]-S[sub 2]CPMe[sub 3])(CO)[sub 2](PMe[sub 3])[sub 2], [Mo([eta][sup 2]-S[sub 2]C(H)PMe[sub 3])(CO)[sub 2](PMe[sub 3])[sub 2]]BF[sub 4], and [Mo([eta][sup 3]-SC(SMe)PMe[sub 3])(CO)[sub 2](PMe[sub 3])[sub 2]]I