Thursday, November 11, 2010: 2:15 PM
253 B Room (Salt Palace Convention Center)
Density functional theory and Bader charge analysis were used to investigate the charge state of atomic hydrogen, oxygen, and nitrogen in vanadium, niobium, and tantalum metals. Over a range of concentrations and hydrogen-site configurations it is found that hydrogen consistently acquires a net charge of -0.6e in the pure group 5 metals compared with a significantly smaller value of 0.3e in palladium. Although there is indirect evidence that the electronic charge plays a role in the solubility and diffusivity of hydrogen in the group 5 metals, this is the first work to quantify the value of the charge. Hydrogen tends to migrate to regions of the metal lattice that minimize its overall charge density, which generally corresponds to the T-site in the bcc metals. It is found that the charge of hydrogen at the O-site of vanadium can be slightly lower due to lattice deformation and may explain the occupation of both T- and O-sites in vanadium-hydrides. Results will be presented on atomic hydrogen, oxygen, and nitrogen solubilities in Group V metals as a function of gas concentration.