Dislocation loop formation by swift heavy ion irradiation of metals

Khara, Galvin S; Murphy, Samuel T.; Duffy, Dorothy M.

doi:10.1088/1361-648x/aa74f8

Cited by 18 publications

(26 citation statements)

References 49 publications

(61 reference statements)

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“…For bulk tungsten, the number of defects is expected to follow a linear trend [29] with S e , but for nanowires the behaviour is quite different as identified from the curves in figure 8. Starting with the TNW (blue line), there is an increase in the number of vacancies from 7.4 to 10.7 keV nm −1 , then it decreases until the hole keeps open and increases again.…”

Section: Resultsmentioning

confidence: 88%

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MeV irradiation of tungsten nanowires: structural modifications

Grossi

Kohanoff

Bringa

2020

Mater. Res. Express

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In this work we use the Two Temperature Model coupled to Molecular Dynamics (TTM-MD) to study swift heavy ion irradiation of W finite nanowires. Au projectiles are considered with energies ranging from 20 to 50 MeV, which correspond to electronic stopping values less than 20 keV nm −1 in the regime where electronic stopping is larger than nuclear stopping. Nanowires with diameters much smaller than the electron mean free path are considered for two different sizes with an aspect ratio ∼3.7 between length and diameter. Nanowires display radiation-induced surface roughening, sputtering yields and the formation of point defects and di-vacancies. For the smallest size, a hole stays opened in the central part of the wire for S e > 12.6 keV nm −1 . W nanofoams, considered as collections of connected nanowires like those simulated here, are expected to behave similarly under irradiation displaying radiation resistance for the electronic stopping range that has been considered. In fact, nanowires larger than tens of nm would be needed for defect accumulation and lack of radiation resistance.

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Section: Resultsmentioning

confidence: 88%

“…The TTM-MD model [28,29] pretends to describe the process by which a SHI traverses a material and leaves highly excited electrons in its path. For this purpose, a track with an elevated electronic temperature (T e ) is used to represent the energy lost by the ion with a given electronic stopping power (S e ).…”

Section: Methodsmentioning

confidence: 99%

MeV irradiation of tungsten nanowires: structural modifications

Grossi

Kohanoff

Bringa

2020

Mater. Res. Express

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“…This is an intermediate value for the diameter according to a range of values between 2-3 nm [63,64]. This cylindrical initial profile has been replaced by Gaussian or other similar profiles in related works [65,66]. Since the irradiation is perpendicular to the wire, the length of the track L track corresponds to the diameter of the NW.…”

Section: Methodsmentioning

confidence: 99%

“…To give a realistic description of the electronic thermal transport away from the ion track, the electronic cell has been extended beyond the MD cell to enable the transport of the electronic energy away from the simulation cell (MD cell) [65,66] (this is also considered for cascade simulations [10,12]). The energy diffusion out of the nanowire would depend on the environment where it is being studied.…”

Section: Methodsmentioning

confidence: 99%

Electronic heat transport versus atomic heating in irradiated short metallic nanowires

et al. 2019

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The two-temperature model (TTM) is commonly used to represent the energy exchange between atoms and electrons in materials under irradiation. In this work we use the TTM coupled to molecular dynamics (TTM-MD) to study swift heavy ion irradiation of Au and W finite nanowires. While no permanent structural modifications are observed in bulk, nanowires behave in a different way depending on thermal conductivity and the electronphonon coupling parameter. Au is a good heat conductor and it does not transfer energy from electrons to phonons too efficiently. Therefore, energy is quickly carried away from the track so that both electronic and lattice temperatures remain quite uniform across the sample at all times. W has a lower thermal conductivity and a larger electron-phonon coupling, thus supporting an inhomogeneous lattice temperature profile with temperatures well above melting lasting several picoseconds in the irradiated region. Both W and Au nanowires display radiation-induced surface roughening. However, in the case of W there is also sputtering and the formation of a hole in the central part of the wire, purely due to the energy transferred to the atoms by the electrons. The physical mechanisms underlying these findings are rationalized in terms of a combination of sputtering, vacancy formation, and melt flow phenomena. The role of the electron-phonon coupling parameter g is analyzed.

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“…The first 2T-MD simulations of SHI used a simple deposition model and investigated the effect of varying the heat capacity and thermal conductivity on the number of residual defects, in order to investigate conditions under which electrons were acting as storage or dissipation mechanisms [61]. More recent simulations on bcc and fcc metals found that Fe was more susceptible to SHI damage than W [62] due to both the lower melting temperature and higher electron-phonon coupling of Fe. An interesting feature of the damage created in both metals was the creation of interstitial type dislocation loops close to, and oriented along, the ion path.…”

Section: Shi Irradiationmentioning

confidence: 99%

Modelling radiation effects in solids with two-temperature molecular dynamics

Darkins

Duffy

2018

Computational Materials Science

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The ability to predict the structural modifications of materials resulting from a broad range of irradiation scenarios would have a positive impact on many fields of science and technology. Established techniques for modelling large atomic systems, such as classical molecular dynamics, are limited by the neglect of the electronic degrees of freedom which restricts their application to irradiation events that primarily interact with atomic nuclei. Ab initio methods, on the other hand, include electronic degrees of freedom, but the requisite computational costs restrict their application to relatively small systems. Recent methodological developments aimed at overcoming some of these limitations are based on methods that couple atomistic models to a continuum model for the electronic energy, where energy is exchanged between the nuclei and electrons via electronic stopping and electron-phonon coupling mechanisms. Such two-temperature molecular dynamics models, as they are known, make it practicable to simulate the effects of electronic excitations on systems with millions, or even hundreds of millions, of atoms. They have been used to study laser irradiation of metallic films, swift heavy ion irradiation of metals and semiconductors, and moderately high ion irradiation of metals. In this review we describe the two-temperature molecular dynamics methodology and the various practical considerations required for its implementation. We provide example applications of the model to multiple irradiation scenarios that accommodate electronic excitations. We also describe the challenges of including the effects of the modification of the interatomic interactions, due to the excitation of electrons, in the simulations and how these challenges can be overcome.

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Dislocation loop formation by swift heavy ion irradiation of metals

Cited by 18 publications

References 49 publications

MeV irradiation of tungsten nanowires: structural modifications

MeV irradiation of tungsten nanowires: structural modifications

Electronic heat transport versus atomic heating in irradiated short metallic nanowires

Modelling radiation effects in solids with two-temperature molecular dynamics

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