Examination of the impact of electron–phonon coupling on fission enhanced diffusion in uranium dioxide using classical molecular dynamics

2015 ◽  
Vol 30 (9) ◽  
pp. 1485-1494 ◽  
Author(s):  
Jonathan L. Wormald ◽  
Ayman I. Hawari
Keyword(s):  
Molecular Dynamics ◽  
Uranium Dioxide ◽  
Phonon Coupling ◽  
Enhanced Diffusion ◽  
Classical Molecular Dynamics ◽  
Electron Phonon Coupling ◽  
Image Position ◽  
The Impact

Abstract

Experimental Determination of the Relationship Between Thermal Boundary Resistance and Non-Abrupt Interfaces and Electron-Phonon Coupling

Volume 4 ◽  
2004 ◽  
Author(s):  
Robert J. Stevens ◽  
Pamela M. Norris ◽  
Arthur W. Lichtenberger
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Room Temperature ◽  
Energy Transport ◽  
Boundary Resistance ◽  
Thermal Boundary Resistance ◽  
Phonon Coupling ◽  
Thermal Boundary Conductance ◽  
Electron Phonon Coupling ◽  
The Impact

Understanding thermal boundary resistance (TBR) is becoming increasingly important for the thermal management of micro and optoelectronic devices. The current understanding of room temperature TBR is often not adequate for the thermal design of tomorrow’s complex micro and nano devices. Theories have been developed to explain the resistance to energy transport by phonons across interfaces. The acoustic mismatch model (AMM) [1, 2], which has had success at explaining low temperature TBR, does not account for the high frequency phonons and imperfect interfaces of real devices at room temperature. The diffuse mismatch model (DMM) was developed to account for real surfaces with higher energy phonons [3, 4]. DMM assumes that all phonons incident on the interface from both sides are elastically scattered and then emitted to either side of the interface. The probability that a phonon is emitted to a particular side is proportional to the phonon density of states of the two interface materials. Inherent to the DMM is that the transport is independent of the interface structure itself and is only dependent on the properties of the two materials. Recent works have shown that the DMM does not adequately capture all the energy transport mechanisms at the interface [5, 6]. In particular, the DMM under-predicts transport across interfaces between non Debye-like materials, such at Pb and diamond, by approximately an order of magnitude. The DMM also tends to over-predict transport for interfaces made with materials of similar acoustic properties, Debye-like materials. There have been several explanations and models developed to explain the discrepancies between the mismatch models and experimental data. Some of these models are based on modification of the AMM and DMM [7–9]. Other works have utilized lattice-dynamical modeling to calculate phonon transmission coefficients and thermal boundary conductivities for abrupt and disordered interfaces [3, 6, 10–13]. Recent efforts to better understand room temperature TBR have utilized molecular dynamics simulations to account for more realistic anharmonic materials and inelastic scattering [14–18]. Models have also been developed to account for electron-phonon scattering and its effect on the thermal boundary conductance for interfaces with one metal side [19–22]. Although there have been numerous thermal boundary resistance theoretical developments since the introduction of the AMM, there still is not an unifying theory that has been well validated for high temperature solid-solid interfaces. Most of the models attempt to explain some of the experimental outliers, such as Pb/diamond and TiN/MgO interfaces [6, 23], but have not been fully tested for a range of experimental data. Part of the problem lies in the fact that very little reliable data is available, especially data that is systematically taken to validate a particular model. To this end, preliminary measurements of TBR are being made on a series of metal on non-metal substrate interfaces using a non-destructive optical technique, transient thermal reflectance (TTR) described in Stevens et al. [5]. Initial testing examines the impact of different substrate preparation and deposition conditions on TBR for Debye-like interfaces for which TBR should be small for clean and abrupt interfaces. Variables considered include sputter etching power and duration, electron beam source clean, and substrate temperature control. The impact of alloying and non-abrupt interfaces on the TBR is examined by fabricating interfaces of both Debye-like and non Debye-like interfaces followed by systematically measuring TBR and altering the interfaces by annealing the samples to increase the diffusion depths at the interfaces. Inelastic electron scattering at the interface has been proposed by Hubermann et al. and Sergeev to decrease TBR at interfaces [19–21]. Two sets of samples are prepared to examine the electron-phonon connection to improved thermal boundary conductance. The first consists of thin Pt and Ag films on Si and sapphire substrates. Pt and Ag electron-phonon coupling factors are 60 and 3.1×1016 W/m3K respectively. Both Pt and Ag have similar Debye temperatures, so electron scattering rates can be examined without much change in acoustic effects. The second electron scattering sample series consist of multiple interfaces fabricated with Ni, Ge, and Si to separate the phonon and electron portions of thermal transport. The experimental data is compared to several of the proposed theories.

Including the Effects of Electronic Excitations and Electron-Phonon Coupling in Cascade Simulations

2006 ◽  
Vol 981 ◽  
Author(s):  
Dorothy Duffy ◽  
Alexis Rutherford
Keyword(s):  
Molecular Dynamics ◽  
Electronic System ◽  
High Energy ◽  
Heat Diffusion ◽  
Dynamics Simulation ◽  
Electronic Excitations ◽  
Phonon Coupling ◽  
Electronic Temperature ◽  
Heat Diffusion Equation ◽  
Electron Phonon Coupling

AbstractRadiation damage has traditionally been modeled using cascade simulations however such simulations generally neglect the effects of electron-ion interactions, which may be significant in high energy cascades. A model has been developed which includes the effects of electronic stopping and electron-phonon coupling in Molecular Dynamics simulations by means of an inhomogeneous Langevin thermostat. The energy lost by the atoms to electronic excitations is gained by the electronic system and the energy evolution of the electronic system is modeled by the heat diffusion equation. Energy is exchanged between the electronic system and the atoms in the Molecular Dynamics simulation by means of a Langevin thermostat, the temperature of which is the local electronic temperature. The model is applied to a 10 keV cascade simulation for Fe.

scholarly journals Correlating structural dynamics and catalytic activity of AgAu nanoparticles with ultrafast spectroscopy and all-atom molecular dynamics simulations

2018 ◽  
Vol 208 ◽  
pp. 269-286 ◽  
Author(s):  
G. F. Ferbonink ◽  
T. S. Rodrigues ◽  
D. P. dos Santos ◽  
P. H. C. Camargo ◽  
R. Q. Albuquerque ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Dynamics ◽  
Ultrafast Spectroscopy ◽  
Surface Segregation ◽  
Core Shell ◽  
Hollow Core ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Equilibrium Structures ◽  
Dynamics Simulations

Electron–phonon coupling times, equilibrium structures and surface segregation as a function of hollow core–shell AgAu nanoparticle composition.

scholarly journals Electronic Nature of Charge Density Wave and Electron-Phonon Coupling in Kagome Superconductor KV3Sb5

2021 ◽  
Author(s):  
Xingjiang Zhou ◽  
Hai-Lan Luo ◽  
Qiang Gao ◽  
Hongxiong Liu ◽  
Yuhao Gu ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Fermi Surface ◽  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Anomalous Hall Effect ◽  
Phonon Coupling ◽  
Electronic Nature ◽  
Electron Phonon Coupling ◽  
The Impact

Abstract The Kagome superconductors AV3Sb5 (A=K, Rb, Cs) have received enormous attention due to their nontrivial topological electronic structure, anomalous physical properties and superconductivity. Unconventional charge density wave (CDW) has been detected in AV3Sb5 that is found to be intimately intertwined with the anomalous Hall effect and superconductivity. High-precision electronic structure determination is essential to understand the origin of the CDW transition and its interplay with electron correlation, topology and superconductivity, yet, little evidence has been found about the impact of the CDW state on the electronic structure in AV3Sb5. Here we unveil electronic nature of the CDW phase in our high-resolution angle-resolved photoemission (ARPES) measurements on KV3Sb5. We have observed CDW-induced Fermi surface reconstruction and the associated band structure folding. The CDW-induced band splitting and the associated gap opening have been revealed at the boundary of the pristine and reconstructed Brillouin zone. The Fermi surface- and momentum-dependent CDW gap is measured for the first time and the strongly anisotropic CDW gap is observed for all the V-derived Fermi surface sheets. In particular, we have observed signatures of the electron-phonon coupling for all the V-derived bands. These results provide key insights in understanding the nature of the CDW state and its interplay with superconductivity in AV3Sb5 superconductors.

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