Significance of self-trapping on hydrogen diffusion
Andreas Blomqvist1, Gunnar K Pálsson, C Moysés Araújo
1Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala, Sweden.
Physical Review Letters
|January 15, 2011
Summary
Hydrogen diffusion in niobium (Nb) is hindered by lattice strain at low temperatures. At higher temperatures, this strain effect lessens, increasing hydrogen
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Hydrogen diffusion in transition metals like niobium is crucial for applications.
- Understanding the temperature-dependent behavior of hydrogen in niobium is complex.
- Existing models may not fully capture the microstructural interactions at elevated temperatures.
Purpose of the Study:
- To investigate the diffusion rate of hydrogen in niobium.
- To elucidate the role of lattice strain in hydrogen diffusion.
- To re-evaluate the conceptual framework for hydrogen diffusion in transition metals.
Main Methods:
- Utilizing ab initio molecular dynamics simulations.
- Analyzing the interaction between hydrogen and the niobium lattice.
- Calculating hydrogen residence times and hopping rates at various temperatures.
Main Results:
- At low temperatures, hydrogen is significantly trapped by local strain fields in the niobium lattice.
- At elevated temperatures (>400 K), the residence time of hydrogen is insufficient to develop the strain field.
- This reduced interaction leads to an increased hopping rate (1/τ) of hydrogen.
Conclusions:
- The conceptual framework for hydrogen diffusion in transition metals needs revision.
- Lattice strain plays a dynamic role in hydrogen diffusion, especially at lower temperatures.
- The findings provide new insights into hydrogen transport mechanisms in metals.
Related Concept Videos
00:26Hydrogen Bonds
Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a partial negative charge. The other is a hydrogen atom that has bonded with another electronegative atom and has a partial positive charge.Hydrogen Bonds Control the World!Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are...
01:04Hydrogen Bonds
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another polar molecule, such as water (H2O), hydrogen fluoride (HF), or ammonia (NH3). The huge electronegativity difference between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for an N atom), combined with the very small size of an H atom...
02:13Reduction of Alkenes: Catalytic Hydrogenation
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
01:29Chain Reactions
Chain reactions involve highly reactive transient species, such as atoms or free radicals, as intermediates. These intermediates facilitate rapid reactions over an extended period. The process includes a series of steps: a reactive intermediate is consumed, reactants are converted to products, and the intermediate is regenerated. This cycle enables continuous repetition, amplifying the production of products with a small amount of intermediate. Chain reactions often utilize free radicals as...
01:33Radical Reactivity: Intramolecular vs Intermolecular
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak carbon–halogen...
01:12Double Resonance Techniques: Overview
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...