Higher hydrides of vanadium and niobium

Reilly, J.J.; Wiswall, R.H.

doi:10.1021/ic50089a013

Cited by 291 publications

(159 citation statements)

References 1 publication

Supporting

Mentioning

133

Contrasting

Order By: Relevance

“…5(a)] is the most stable enthalpically, which is in good agreement with the experimental results these again being at room temperature. 25 Above 50 GPa, an orthorhombic Pnma structure [Z = 4, Fig. 5(b)] is then preferred.…”

Section: Nbhmentioning

confidence: 99%

See 1 more Smart Citation

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

et al. 2013

View full text Add to dashboard Cite

As part of a search for enhanced superconductivity, we explore theoretically the ground-state structures and properties of some hydrides of niobium over a range of pressures and particularly those with significant hydrogen content. A primary motivation originates with the observation that under normal conditions niobium is the element with the highest superconducting transition temperature (T c ), and moreover some of its compounds are metals again with very high T c 's. Accordingly, combinations of niobium with hydrogen, with its high dynamic energy scale, are also of considerable interest. This is reinforced further by the suggestion that close to its insulator-metal transition, hydrogen may be induced to enter the metallic state somewhat prematurely by the addition of a relatively small concentration of a suitable transition metal. Here, the methods used correctly reproduce some ground-state structures of niobium hydrides at even higher concentrations of niobium. Interestingly, the particular stoichiometries represented by NbH 4 and NbH 6 are stabilized at fairly low pressures when proton zero-point energies are included. While no paired H 2 units are found in any of the hydrides we have studied up to 400 GPa, we do find complex and interesting networks of hydrogens around the niobiums in high-pressure NbH 6 . The Nb-Nb separations in NbH n are consistently larger than those found in Nb metal at the respective pressures. The structures found in the ground states of the high hydrides, many of them metallic, suggest that the coordination number of hydrogens around each niobium atom grows approximately as 4n in NbH n (n = 1-4), and is as high as 20 in NbH 6 . NbH 4 is found to be a plausible candidate to become a superconductor at high pressure, with an estimated T c ∼ 38 K at 300 GPa.

show abstract

Section: Nbhmentioning

confidence: 99%

“…At about 2 atm, NbH 2 (the δ phase) has been synthesized by a direct reaction 25 of hydrogen with Nb metal, and also by using an aqueous electrolytic method. 26 NbH 2 has the common CaF 2 type structure, where the Nb metal forms an fcc structure and the H atoms occupy all the T sites of the fcc lattice.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The γ phase for the pure V metal was also reported to have the FCC structure. 15) Figure 5 shows the lattice parameter changes and the Thus, the a-and c-axial changes in transformation from the β phases to the γ phases increase with decreasing the c/a of the β phases. Moreover, the a-axes contract in the absorbing process and expand in the desorbing process as opposed to the c-axes.…”

Section: Protium Storage Properties and Protide Structures Inmentioning

confidence: 99%

Effects of Protide Structures on Hysteresis in Ti-Cr-V Protium Absorption Alloys

et al. 2002

View full text Add to dashboard Cite

Ti-Cr-V alloys have a higher protium (hydrogen atom) desorption capacity, but a larger hysteresis in the absorption and desorption processes than AB 2 and AB 5 type protium absorption alloys. It is desirable that the alloys have a smaller hysteresis for the use of hydrogen storage tanks. This paper aims to clarify the effects of protide (hydride) structures on the hysteresis in Ti-Cr-V protium absorption alloys. It was found that the β phases observed after desorbing at the desorption plateau region had the BCC structure for the alloys (Ti:Cr = 2:3) containing less than 70 at%V, but the BCT structure for the alloys (Ti:Cr = 2:3) containing more than 70 at%V. A major reason for the large hysteresis in the Ti-Cr-V alloys appears to be the a-axial contraction in the absorbing process and the a-axial expansion in the desorbing process as opposed to the c-axial changes.

show abstract

“…14 While the present spinpolarized calculations are very time consuming, preventing us from addressing these subsequent stages of the sorption process in the present article, it is worthy to note that experimentally, V hydride was reported to decompose easily even though V displays a high affinity for hydride formation. 32,33 The reaction ͑VH 2 → V+2H͒ was reported to occur at 35 C with an activation barrier of 0.04 eV for the diffusion of atomic H from free V surface. 34 Subsequently, the atomic H transfers to Mg atoms, forming MgH 2 around the V site and, thus, V can be regarded as an "atomic hydrogen pump," which facilitates the adsorption of atomic H. While our results presented herein shed light on the nature of the initial surface adsorption of hydrogen onto V sites in the Mg surface, they do not provide a full rationalization of the experimentally observed catalytic role of V for hydrogen sorption into ball milled Mg nanocomposite materials.…”

mentioning

confidence: 99%

The role of V2O5 on the dehydrogenation and hydrogenation in magnesium hydride: An ab initio study

Smith

Yao

et al. 2008

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

Higher hydrides of vanadium and niobium

Cited by 291 publications

References 1 publication

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

Effects of Protide Structures on Hysteresis in Ti-Cr-V Protium Absorption Alloys

The role of V2O5 on the dehydrogenation and hydrogenation in magnesium hydride: An ab initio study

Contact Info

Product

Resources

About