Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

2010 ◽  
Vol 25 (2) ◽  
pp. 315-327 ◽  
Author(s):  
Donald F. Johnson ◽  
Emily A. Carter
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Fusion Reactors ◽  
Adsorbed Hydrogen ◽  
Functional Theory ◽  
Outward Diffusion ◽  
Vacancy Trapping ◽  
High Energy Particles ◽  
Interaction Surface

Understanding the interaction between atomic hydrogen and solid tungsten is important for the development of fusion reactors in which proposed tungsten walls would be bombarded with high energy particles including hydrogen isotopes. Here, we report results from periodic density-functional theory calculations for three crucial aspects of this interaction: surface-to-subsurface diffusion of H into W, trapping of H at vacancies, and H-enhanced decohesion, with a view to assess the likely extent of hydrogen isotope incorporation into tungsten reactor walls. We find energy barriers of (at least) 2.08 eV and 1.77 eV for H uptake (inward diffusion) into W(001) and W(110) surfaces, respectively, along with very small barriers for the reverse process (outward diffusion). Although H dissolution in defect-free bulk W is predicted to be endothermic, vacancies in bulk W are predicted to exothermically trap multiple H atoms. Furthermore, adsorbed hydrogen is predicted to greatly stabilize W surfaces such that decohesion (fracture) may result from high local H concentrations.

scholarly journals The Stone–Wales transformation: from fullerenes to graphite, from radiation damage to heat capacity

2016 ◽  
Vol 374 (2076) ◽  
pp. 20150317 ◽  
Author(s):  
M. I. Heggie ◽  
G. L. Haffenden ◽  
C. D. Latham ◽  
T. Trevethan
Keyword(s):  
Heat Capacity ◽  
Density Functional ◽  
Local Density ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Functional Theory ◽  
High Temperature Heat Capacity ◽  
Bond Rotation ◽  
Buckminster Fullerene ◽  
Equilibrium Concentrations

The Stone–Wales (SW) transformation, or carbon-bond rotation, has been fundamental to understanding fullerene growth and stability, and ab initio calculations show it to be a high-energy process. The nature and topology of the fullerene energy landscape shows how the I h -C 60 must be the final product, if SW transformations are fast enough, and various mechanisms for their catalysis have been proposed. We review SW transformations in fullerenes and then discuss the analogous transformation in graphite, where they form the Dienes defect, originally posited to be a transition state in the direct exchange of a bonded atom pair. On the basis of density functional theory calculations in the local density approximation, we propose that non-equilibrium concentrations of the Dienes defect arising from displacing radiation are rapidly healed by point defects and that equilibrium concentrations of Dienes defects are responsible for the divergent ultra-high-temperature heat capacity of graphite. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’.

scholarly journals Density Functional Theory Calculations on Nitrated Boroxines as Possible High Energy-Density Materials

2017 ◽  
Vol 117 (2) ◽  
pp. 27 ◽  
Author(s):  
Lisa M. Ina ◽  
David W. Ball
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Minimum Energy ◽  
Normal Modes ◽  
Density Functional Theory Calculations ◽  
Combustion Products ◽  
High Energy ◽  
High Energy Density ◽  
Energy Materials ◽  
Functional Theory

Density functional theory calculations were performed on a series of nitroboroxine molecules (cyclo-[BO]3-[NO2]xH3-x, x = 1 – 3) to determine their thermodynamic properties and assess them as potential high energy materials.  Minimum-energy geometries of four boroxine molecules were determined, along with their normal modes of vibration.  Analysis of the energies of the molecules and their possible decomposition and combustion products suggests an energy contact comparable to that of TNT.

scholarly journals Nanometer-size Na cluster formation in micropore of hard carbon as origin of higher-capacity Na-ion battery

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yong Youn ◽  
Bo Gao ◽  
Azusa Kamiyama ◽  
Kei Kubota ◽  
Shinichi Komaba ◽  
...  
Keyword(s):  
Density Functional ◽  
Cluster Formation ◽  
High Capacity ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
High Energy Density ◽  
Hard Carbon ◽  
Functional Theory ◽  
Nanometer Size ◽  
Li Ion

AbstractDevelopment of high-energy-density anode is crucial for practical application of Na-ion battery as a post Li-ion battery. Hard carbon (HC), though a promising anode candidate, still has bottlenecks of insufficient capacity and unclear microscopic picture. Usage of the micropore has been recently discussed, however, the underlying sodiation mechanism is still controversial. Herein we examined the origin for the high-capacity sodiation of HC, based on density functional theory calculations. We demonstrated that nanometer-size Na cluster with 3–6 layers is energetically stable between two sheets of graphene, a model micropore, in addition to the adsorption and intercalation mechanisms. The finding well explains the extended capacity over typical 300 mAhg−1, up to 478 mAhg−1 recently found in the MgO-templated HC. We also clarified that the MgO-template can produce suitable nanometer-size micropores with slightly defective graphitic domains in HC. The present study considerably promotes the atomistic theory of sodiation mechanism and complicated HC science.

scholarly journals A new 2D auxetic CN2 nanostructure with high energy density and mechanical strength

2021 ◽  
Vol 23 (7) ◽  
pp. 4353-4364
Author(s):  
Qun Wei ◽  
Ying Yang ◽  
Alexander Gavrilov ◽  
Xihong Peng
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Energy Density ◽  
Mechanical Strength ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
High Energy Density ◽  
Two Dimensional ◽  
Functional Theory

The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dynamics (AIMD) and density-functional theory calculations.

scholarly journals Topological Anderson Insulator in Cation-Disordered Cu2ZnSnS4

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2595
Author(s):  
Binayak Mukherjee ◽  
Eleonora Isotta ◽  
Carlo Fanciulli ◽  
Narges Ataollahi ◽  
Paolo Scardi
Keyword(s):  
Density Functional ◽  
Surface States ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Material System ◽  
Slab Geometry ◽  
Functional Theory ◽  
Cation Disorder ◽  
Real Material ◽  
Reactive Mechanical Alloying

We present the first candidate for the realization of a disorder-induced Topological Anderson Insulator in a real material system. High-energy reactive mechanical alloying produces a polymorph of Cu2ZnSnS4 with high cation disorder. Density functional theory calculations show an inverted ordering of bands at the Brillouin zone center for this polymorph, which is in contrast to its ordered phase. Adiabatic continuity arguments establish that this disordered Cu2ZnSnS4 can be connected to the closely related Cu2ZnSnSe4, which was previously predicted to be a 3D topological insulator, while band structure calculations with a slab geometry reveal the presence of robust surface states. This evidence makes a strong case in favor of a novel topological phase. As such, the study opens up a window to understanding and potentially exploiting topological behavior in a rich class of easily-synthesized multinary, disordered compounds.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

2019 ◽  
Author(s):  
Anshuman Kumar ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Cd Spectra ◽  
Functional Theory ◽  
Polyproline Ii ◽  
Solvent Dependence ◽  
Explicit Consideration ◽  
New Interpretation ◽  
Implicit And Explicit ◽  
Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

Sign in / Sign up

Export Citation Format

Share Document