Helium Interaction with Y2Ti2O7: A First Principles Study

2014 ◽  
Vol 1645 ◽  
Author(s):  
Thomas Danielson ◽  
Celine Hin
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Great Promise ◽  
Functional Theory ◽  
Ferritic Alloys ◽  
Helium Bubbles ◽  
Helium Clusters ◽  
Helium Embrittlement ◽  
Materials Used ◽  
Trapping Sites

ABSTRACTHelium embrittlement poses a great threat to materials used in both fusion and fissionreactor systems due to (n,α) transmutation reactions. Because of this, materials capable of moderating the helium content reaching grain boundaries and voids must be developed and improved to prevent catastrophic failure of reactor materials. Nanostructured ferritic alloys (NFAs) have shown great promise in preventing helium embrittlement due to the large number density of nanoscale precipitates acting as trapping sites for helium clusters and helium bubbles. In this study, we present density functional theory calculations on the interaction of helium with nanoscale precipitates found in NFAs as a preliminary study to furthering our understanding of the energetic mechanisms causing the precipitates to act as trapping sites for helium.

scholarly journals The effect of helium nano-bubbles on the structures stability and electronic properties of palladium tritides: a density functional theory study

2014 ◽  
Vol 470 (2171) ◽  
pp. 20140357 ◽  
Author(s):  
N. K. Das ◽  
K. Rigby ◽  
N. H. de Leeuw
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Perfect Lattice ◽  
Helium Atoms ◽  
Helium Clusters ◽  
Octahedral Sites ◽  
Metal Atoms

Density functional theory calculations have been used to study the incorporation of helium in perfect and defect-containing palladium tritides, where we have calculated the energetics of incorporation and the migration behaviour. Helium atoms preferably occupy the octahedral interstitial and substitutional sites in the perfect and Pd vacancy-containing tritides, respectively. The energetics reveal that helium clusters can form in the lattice, which displace the Pd metal atoms. The defective lattice shows less expansion compared with the perfect lattice, which can accommodate the helium less easily. The path from octahedral–tetrahedral–octahedral sites is the lowest energy pathway for helium diffusion, and the energetics indicate that the helium generated from tritium decay can accumulate in or near the octahedral sites. Density of states analyses shows the hybridization between palladium d and tritium s orbitals and repulsion between palladium d and helium s orbitals, which can distort the lattice as a result of generating localized stress.

scholarly journals Computationally aided, entropy-driven synthesis of highly efficient and durable multi-elemental alloy catalysts

2020 ◽  
Vol 6 (11) ◽  
pp. eaaz0510 ◽  
Author(s):  
Yonggang Yao ◽  
Zhenyu Liu ◽  
Pengfei Xie ◽  
Zhennan Huang ◽  
Tangyuan Li ◽  
...  
Keyword(s):  
Density Functional ◽  
Rational Design ◽  
Density Functional Theory Calculations ◽  
Great Promise ◽  
Alloy Formation ◽  
Functional Theory ◽  
Excellent Thermal Stability ◽  
Design And Synthesis ◽  
Highly Efficient ◽  
Computational Strategy

Multi-elemental alloy nanoparticles (MEA-NPs) hold great promise for catalyst discovery in a virtually unlimited compositional space. However, rational and controllable synthesize of these intrinsically complex structures remains a challenge. Here, we report the computationally aided, entropy-driven design and synthesis of highly efficient and durable catalyst MEA-NPs. The computational strategy includes prescreening of millions of compositions, prediction of alloy formation by density functional theory calculations, and examination of structural stability by a hybrid Monte Carlo and molecular dynamics method. Selected compositions can be efficiently and rapidly synthesized at high temperature (e.g., 1500 K, 0.5 s) with excellent thermal stability. We applied these MEA-NPs for catalytic NH3 decomposition and observed outstanding performance due to the synergistic effect of multi-elemental mixing, their small size, and the alloy phase. We anticipate that the computationally aided rational design and rapid synthesis of MEA-NPs are broadly applicable for various catalytic reactions and will accelerate material discovery.

Thermo-chemical metastability of multilayer epitaxial graphene oxide: Experiments and density functional theory calculations

2012 ◽  
Vol 1451 ◽  
pp. 39-44
Author(s):  
Si Zhou ◽  
S. Kim ◽  
Y. Hu ◽  
C. Berger ◽  
W. de Heer ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Graphene Oxide ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Epitaxial Graphene ◽  
Great Promise ◽  
Hydroxyl Groups ◽  
Minimal Amount ◽  
Multilayer Graphene ◽  
Functional Theory

ABSTRACTGraphene oxide holds great promise for future applications in nano-technology. The chemistry of this material is not well understood. This understanding is crucial to enable future applications of graphene oxide. In this study, experiments and density functional theory calculations are combined to elucidate the chemical properties of multilayer graphene oxide obtained by oxidizing epitaxial graphene grown on silicon carbide via the Hummers method. This study shows that at room temperature as prepared graphene oxide films exhibit a uniform and homogeneous structure, include a minimal amount of edges and holes, and have an oxidation ratio of about 0.44. The comparison with density-functional calculations shows that graphene oxide includes a minimal amount of intercalated water molecules and well-defined fractions of epoxide and hydroxyl groups.

Migration Barriers and Evolution of Mechanical Properties of Oxide Nanoclusters Containing Helium

2015 ◽  
Vol 1743 ◽  
Author(s):  
Thomas Danielson ◽  
Celine Hin
Keyword(s):  
Mechanical Properties ◽  
Density Functional ◽  
Complex Oxide ◽  
Functional Theory ◽  
Ferritic Alloys ◽  
Helium Concentration ◽  
Migration Barriers ◽  
Bcc Iron ◽  
And Migration ◽  
Trapping Sites

ABSTRACTHigh number densities of complex oxide nanoclusters in nanostructured ferritic alloys have been shown to act as effective trapping sites for the transmutation product helium. Density functional theory has been used to investigate the evolution of the mechanical properties of oxide nanoclusters as helium concentration increases. The migration barrier and migration path of helium in the oxide has also been tested in order to make a comparison with the barriers in BCC iron and offer insight to the helium trapping mechanisms of the oxides.

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.

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.

Is a Non-Transition Element Nitride Ferromagnet Ever Achievable? Indication of the N-N Pairing Instability

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1525-1531 ◽  
Author(s):  
Wojciech Grochala
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Transition Element ◽  
Density Functional Theory Calculations ◽  
Functional Theory

The enthalpy of four polymorphs of CaN has been scrutinized at 0 and 100 GPa using density functional theory calculations. It is shown that structures of diamagnetic calcium diazenide (Ca2N2) are preferred over the cubic ferromagnetic polymorph (CaN) postulated before, both at 0 and 100 GPa.

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