Atomistic Simulation of Formation and Structure of Misfit Dislocations

1990 ◽  
Vol 202 ◽  
Author(s):  
A.S. Nandedkar ◽  
C.S. Murthy ◽  
G.R. Srinivasan
Keyword(s):  
Driving Force ◽  
Energy Barrier ◽  
Atomistic Simulation ◽  
High Energy ◽  
Misfit Dislocations ◽  
Dislocation Configuration ◽  
Au Film ◽  
Spontaneous Formation ◽  
Minimization Technique ◽  
Highly Strained

ABSTRACTIn our earlier work [1] we had reported first theoretical observations of the spontaneous formation of 60° and 90° misfit dislocations in Au/Ni (15.9% mismatch) systems for the (111) and (001) interfaces respectively. Here, we present the analysis of the evolution of the dislocation configuration as it evolves from a highly strained coherent Au film. The driving force for the formation of these misfit dislocations was the reduction in the config-urational energy during the iterative relaxation of the atoms. A finely stepped energy minimization technique was developed to relax the high energy configuration. Misfit dislocations were also obtained for low misfit systems (Pd/Ni - 10% and Pd/Cu - 7.76%), but a modified approach, which is described here, was used for these systems which shows an energy barrier to the formation of dislocations in the low misfit systems.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

Enhancing the energy barrier and hysteresis temperature in two benchtop-stable Ho(III) single-ion magnets

2021 ◽  
Author(s):  
Kexin Jia ◽  
Xixi Meng ◽  
Mengmeng Wang ◽  
Xiaoshuang Gou ◽  
Yu-Xia Wang ◽  
...  
Keyword(s):  
Energy Barrier ◽  
High Energy ◽  
Halogen Anion ◽  
High Energy Barrier

The energy barrier and hysteresis temperature in two benchtop-stable D5h-symmetry HoIII single-ion magnets were significantly enhanced via the variation of halogen anion. The coexistence of high energy barrier of 418...

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Slow magnetic relaxation in dinuclear dysprosium and holmium phenoxide bridged complexes: a Dy2 single molecule magnet with a high energy barrier

2021 ◽  
Author(s):  
Matilde Fondo ◽  
Julio Corredoira-Vázquez ◽  
Ana M. Garcia-Deibe ◽  
Jesus Sanmartin Matalobos ◽  
Silvia Gómez-Coca ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Single Molecule ◽  
Energy Barrier ◽  
Magnetic Relaxation ◽  
High Energy ◽  
Single Molecule Magnet ◽  
High Energy Barrier ◽  
Slow Magnetic Relaxation

Dinuclear [M(H3L1,2,4)]2 (M = Dy, Dy2; M = Ho, Ho2) complexes were isolated from an heptadentate aminophenol ligand. The crystal structures of Dy2·2THF, and the pyridine adducts Dy2·2Py and Ho2·2Py,...

scholarly journals Driving forces on dislocations: finite element analysis in the context of the non-singular dislocation theory

2021 ◽  
Author(s):  
Xiandong Zhou ◽  
Christoph Reimuth ◽  
Peter Stein ◽  
Bai-Xiang Xu
Keyword(s):  
Finite Element ◽  
Dislocation Loop ◽  
Driving Force ◽  
Complex Geometry ◽  
Driving Forces ◽  
Singular Solutions ◽  
Dislocation Model ◽  
Configurational Force ◽  
Element Analysis ◽  
Dislocation Configuration

AbstractThis work presents a regularized eigenstrain formulation around the slip plane of dislocations and the resultant non-singular solutions for various dislocation configurations. Moreover, we derive the generalized Eshelby stress tensor of the configurational force theory in the context of the proposed dislocation model. Based on the non-singular finite element solutions and the generalized configurational force formulation, we calculate the driving force on dislocations of various configurations, including single edge/screw dislocation, dislocation loop, interaction between a vacancy dislocation loop and an edge dislocation, as well as a dislocation cluster. The non-singular solutions and the driving force results are well benchmarked for different cases. The proposed formulation and the numerical scheme can be applied to any general dislocation configuration with complex geometry and loading conditions.

First principle simulation on oxidation mechanism of diethyl ether by nitrogen dioxide

2015 ◽  
Vol 14 (03) ◽  
pp. 1550020 ◽  
Author(s):  
Yuan Yuan ◽  
Wei Hu ◽  
Xuhui Chi ◽  
Cuihua Li ◽  
Dayong Gui ◽  
...  
Keyword(s):  
Diethyl Ether ◽  
Energy Barrier ◽  
Density Functional ◽  
Oxidation Process ◽  
Oxidation Mechanism ◽  
High Energy ◽  
First Principle ◽  
Functional Theory ◽  
The Third ◽  
High Energy Barrier

The oxidation mechanism of diethyl ethers by NO2was carried out using density functional theory (DFT) at the B3LYP/6-31+G (d, p) level. The oxidation process of ether follows four steps. First, the diethyl ether reacts with NO2to produce HNO2and diethyl ether radical with an energy barrier of 20.62 kcal ⋅ mol-1. Then, the diethyl ether radical formed in the first step directly combines with NO2to form CH3CH ( ONO ) OCH2CH3. In the third step, the CH3CH ( ONO ) OCH2CH3was further decomposed into the CH3CH2ONO and CH3CHO with a moderately high energy barrier of 32.87 kcal ⋅ mol-1. Finally, the CH3CH2ONO continues to react with NO2to yield CH3CHO , HNO2and NO with an energy barrier of 28.13 kcal ⋅ mol-1. The calculated oxidation mechanism agrees well with Nishiguchi and Okamoto's experiment and proposal.

scholarly journals A four-coordinate cobalt(II) single-ion magnet with coercivity and a very high energy barrier

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Yvonne Rechkemmer ◽  
Frauke D. Breitgoff ◽  
Margarethe van der Meer ◽  
Mihail Atanasov ◽  
Michael Hakl ◽  
...  
Keyword(s):  
Energy Barrier ◽  
High Energy ◽  
High Energy Barrier ◽  
Very High Energy ◽  
Very High
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