Coherent displacement of atoms during ion irradiation

Nordlund, K.; Keinonen, J.; Ghaly, Mai; Averback, Robert S

doi:10.1038/17983

Cited by 167 publications

(118 citation statements)

References 14 publications

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“…Similar effects have been previously reported to occur in connection with cratering by single atoms and atom clusters and were found to be in good agreement with experiments. 16,17,21,22,48,49 However, single Cu atoms at similar energies have not been previously reported to produce such complex crater features with an appreciable probability, 36 and thus in the current case the effects are associated with the overlap of several heat spikes ͑see also analysis of fluence dependence below͒.…”

Section: Resultsmentioning

confidence: 74%

“…These energies are typical for ion irradiation of materials, and are well known to form heat spikes that can cause massive atom redistribution and relocation, sometimes resulting in cratering. 15,36 The other important result obtained from the PIC simulations is that the ion flux is very high, the total flux ⌫ of both ions and neutrals over all energies being almost ϳ10 25 ions/ cm 2 / s. This flux obtained from PIC may seem very high compared to typical ion irradiation fluxes which are 5-15 orders of magnitude lower 42,43 but a simple estimate from experimental values of the typical currents in arcs on the order of I = 10 A and final crater areas on the order of A = ͑10 m͒ 2 ͑Ref. 3͒ gives a comparable flux of I / e / A =6 ϫ 10 25 ions/ cm 2 / s ͑e is the electron charge͒.…”

Section: Resultsmentioning

confidence: 99%

“…21,[34][35][36] The ion flux was modeled selecting the impact times randomly in the Poisson distribution 37 such that the average flux corresponded to the one simulated with PIC. The energies were generated in a random distribution corresponding exactly to that obtained from the PIC simulations and the impact positions on the surface were generated randomly within a circle of radius r =3-25 nm.…”

Section: B Simulationsmentioning

confidence: 99%

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Mechanism of surface modification in the plasma-surface interaction in electrical arcs

et al. 2010

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Electrical sparks and arcs are plasma discharges that carry large currents and can strongly modify surfaces. This damage usually comes in the form of micrometer-sized craters and frozen-in liquid on the surface. Using a combination of experiments, plasma and atomistic simulation tools, we now show that the observed formation of deep craters and liquidlike features during sparking in vacuum is explained by the impacts of energetic ions, accelerated under the given conditions in the plasma sheath to kiloelectron volt energies, on surfaces. The flux in arcs is so high that in combination with kiloelectron volt energies it produces multiple overlapping heat spikes, which can lead to cratering even in materials such as Cu, where a single heat spike normally does not.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: B Simulationsmentioning

confidence: 99%

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Mechanism of surface modification in the plasma-surface interaction in electrical arcs

et al. 2010

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“…12 Likewise, the interactions of these shockwaves with a free surface can lead to the surface roughening and creation of huge vacancy dislocation loops. 15,16 In the 0.25-ps snapshot, one can see that the sonic wave propagates without creating low-density regions. For this reason, the supersonic regime is often considered destructive, whereas the sonic regime is considered non-destructive.…”

Section: Resultsmentioning

confidence: 99%

Atomistic material behavior at extreme pressures

2016

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Computer simulations are routinely performed to model the response of materials to extreme environments, such as neutron (or ion) irradiation. The latter involves high-energy collisions from which a recoiling atom creates a so-called atomic displacement cascade. These cascades involve coordinated motion of atoms in the form of supersonic shockwaves. These shockwaves are characterized by local atomic pressures 415 GPa and interatomic distances o 2 Å. Similar pressures and interatomic distances are observed in other extreme environment, including short-pulse laser ablation, high-impact ballistic collisions and diamond anvil cells. Displacement cascade simulations using four different force fields, with initial kinetic energies ranging from 1 to 40 keV, show that there is a direct relationship between these high-pressure states and stable defect production. An important shortcoming in the modeling of interatomic interactions at these short distances, which in turn determines final defect production, is brought to light. INTRODUCTIONAs scientific computing becomes evermore ubiquitous, it is common practice to simulate the effect of extreme environments on materials using molecular dynamics (MD). The ability to capture a material's response atom by atom has helped understand and complement experiments. For example, thanks to MD, the thermodynamic processes that control the production of nanoparticules after pulsed laser irradiation are relatively well understood. 1 Notably, such computational results explain the Newton rings observed in experiments. 2,3 MD also led to a better understanding of the nature of the destructive shockwaves that follow high-energy impact 4-6 and the behavior of materials at high pressure in diamond anvil cells. 7-9 It can predict many properties, such as the Hugoniot, dislocation densities after impact and fracture behavior. In the case of neutron and ion irradiation, MD can be used to predict the evolution of ballistic collisions that occur, and the nature of primary damage produced by the high-energy recoils. 10 It can also shed light on a plethora of mechanisms that take place as the kinetic energy of the recoil is dissipated: fractal replacement sequences, 11 supersonic shockwaves, 12 sonic waves, 12 the formation of liquid-like regions and their recrystallization or amorphization. 13 The aim of many MD studies is to describe the mechanisms and general trends, not to make precise predictions. However, as the scientific community moves towards materials by design and systematic computational characterization, increasingly precise and accurate models are required. In the case of atomistic modeling, methods that explicitly account for electronic structure, such as ab initio MD, are considered the gold standard. Unfortunately, their use has very serious limitations, given their high computational cost. In particular, the simulation of high-energy perturbations such as those involved in neutron or ion irradiation requires large simulation cells: a few hundred thousands of atoms at a minimum...

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“…Ultrafast diffusional dynamics can be studied by classical molecular dynamics (MD) simulations at the atomistic level 10,12,13,14,15,16 . Recently it has been shown by MD studies in accordance with experimental results that under externally forced conditions, transient enhanced intermixing of heavier impurities could occur in bulk materials 17,18 .…”

Section: Introductionmentioning

confidence: 99%

Self-organized transient facilitated atomic transport in Pt∕Al(111)

Süle

2008

The Journal of Chemical Physics

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During the course of atomic transport in a host material, impurity atoms need to surmount an energy barrier driven by thermodynamic bias or at ultra-low temperatures by quantum tunneling. In the present article we demonstrate using atomistic simulations that at ultra-low temperature transient inter-layer atomic transport is also possible without tunneling when the Pt/Al(111) impurity/host system self-organizes itself spontaneously into an intermixed configuration. No such extremely fast athermal concerted process has been reported before at ultra low temperatures. The outlined novel transient atomic exchange mechanism could be of general validity. We find that the source of ultra-low temperature heavy particle barrier crossing is intrinsic and no external bias is necessary for atomic intermixing and surface alloying in Pt/Al although the dynamic barrier height is few eV. The mechanism is driven by the local thermalization of the Al(111) surface in a selforganized manner arranged spontaneously by the system without any external stimulus. The core of the short lived thermalized region reaches the local temperature of ∼ 1000 K (including few tens of Al atoms) while the average temperature of the simulation cell is ∼ 3 K. The transient facilitated intermixing process also takes place with repulsive impurity-host interaction potential leading to negative atomic mobility hence the atomic injection is largely independent of the strength of the impurity-surface interaction. We predict that similar exotic behaviour is possible in other materials as well.

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Coherent displacement of atoms during ion irradiation

Cited by 167 publications

References 14 publications

Mechanism of surface modification in the plasma-surface interaction in electrical arcs

Mechanism of surface modification in the plasma-surface interaction in electrical arcs

Atomistic material behavior at extreme pressures

Self-organized transient facilitated atomic transport in Pt∕Al(111)

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