K. Nordlund

University of Helsinki

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Co-Authors

Flyura Djurabekova

Helsinki Institute of Physics

199

J. Keinonen

University of Helsinki

Arkady V. Krasheninnikov

Helmholtz-Zentrum Dresden-Rossendorf

Jesper Byggmästar

Helsinki Institute of Physics

F. Granberg

Helsinki Institute of Physics

A. Kuronen

Helsinki Institute of Physics

C. Björkas

Royal Military Academy

E. Salonen

University of Oulu

R. S. Averback

University of Illinois Urbana-Champaign

Juha Samela

University of Helsinki

Cooperative Institutions

Culham Science Centre

1,593

Royal Military Academy

1,193

United Kingdom Atomic Energy Authority

851

Culham Centre for Fusion Energy

823

European Organization for Nuclear Research

424

Max Planck Institute for Plasma Physics

395

Max Planck Society

379

CEA Cadarache

377

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

358

Centre National de la Recherche Scientifique

310

Author Statistics

Papers

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Daily and annual modulation rate of low mass dark matter in silicon detectors

Journal of Physics G Nuclear and Particle Physics (2024)

Abolfazl Dinmohammadi Matti Heikinheimo N. Mirabolfathi K. Nordlund Hossein Safari

Abstract Low-threshold solid-state detectors with single electron excitation sensitivity can probe nuclear recoil energies in the sub-100 eV range, coinciding with the typical threshold displacement energies in the detector material. We investigate the daily and annual modulation of the observable event rate for dark matter mass ranging from 0.2 to 5 GeV/c 2 in a silicon detector, considering the energy threshold and the direction of the nuclear recoil. The data for the energy threshold is obtained from a molecular dynamics simulation. It is shown that the directional dependence of the threshold energy and the motion of the laboratory result in the modulation of the interaction event rate. We demonstrate silicon’s average annual interaction rate is more considerable than germanium for low-mass dark matter. However, their event rates take a similar trend in large dark matter masses. Thus, silicon can be a reliable target to discriminate low-mass dark matter from backgrounds. We also find 8 h and 12h periodicities in the time series of event rates for silicon detectors due to the 45-degree symmetry in the silicon crystal structure.

Recoil

Semiconductor detector

10.1088/1361-6471/ad1a76

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Citations (2)

Threshold displacement energy map of Frenkel pair generation in β-Ga2O3 from machine-learning-driven molecular dynamics simulations

Acta Materialia (2024)

Huan He J. Zhao Jesper Byggmästar Ru He K. Nordlund

β-gallium oxide (β-Ga2O3) shows great promise for electronics applications, particularly, in future space operating devices exposed to harsh radiation environments for extended times. This study focuses on crucial, yet not fully explored, aspects of radiation damage in this material, such as threshold displacement energies and formation of various radiation-induced Frenkel pairs. Analyzing over 5,000 molecular dynamics simulations based on our machine-learning potentials, we conclude that the threshold displacement energies for two Ga sites, the tetrahedral (22.9 eV) and octahedral (20 eV) ones, differ stronger than the same values for three different O sites, which range only between 17 eV and 17.4 eV. Mapping of threshold displacement energies unveils significant differences in displacements for all five atomic sites. Our newly developed defect identification methodology successfully classified multiple Frenkel pair types in β-Ga2O3, with over ten different Ga and two primary O ones with a predominant O split interstitial at the O1 site. Finally, the calculated recombination energy barriers suggest that O Frenkel pairs are more likely to recombine upon annealing than Ga. These insights are pivotal for understanding the radiation damage and defect formation in Ga2O3, providing the basis for design of Ga2O3-based electronics with high radiation resistance.

Scalable Vector Graphics

10.1016/j.actamat.2024.120087

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Citations (3)

Magnetic Properties and Diffusion of Adatoms on a Graphene Sheet

Physical Review Letters (2003)

Pekka Lehtinen Adam S. Foster A. Ayuela Arkady V. Krasheninnikov K. Nordlund

We use ab initio methods to calculate the properties of adatom defects on a graphite surface. By applying a full spin-polarized description to the system we demonstrate that these defects have a magnetic moment of about 0.5micro(B) and also calculate its role in diffusion over the surface. The magnetic nature of these intrinsic carbon defects suggests that it is important to understand their role in the recently observed magnetism in pure carbon systems.

Magnetism

10.1103/physrevlett.91.017202

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Citations (438)

Carbon nanotubes as masks against ion irradiation: An insight from atomistic simulations

Applied Physics Letters (2002)

Arkady V. Krasheninnikov K. Nordlund J. Keinonen

Recent experiments show that carbon nanotubes can be used as masks against ion irradiation to make metallic nanowires of a few nanometers in width. In order to ascertain the limitations of this technique, we use molecular dynamics and simulate ion irradiation of multiwalled nanotubes. We derive an equation which for a given nanowire material allows one to estimate the theoretical limit on the minimum width of the wire which can be made using this technique.

Nanometre

Carbon fibers

10.1063/1.1499224

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Citations (38)

Sputter yield reduction and fluence stability of numerically optimized nanocolumnar tungsten surfaces

Physical Review Materials (2023)

C. Cupak A. Lopez-Cazalilla Herbert Biber Johannes Brötzner Martina Fellinger

Nanocolumnar tungsten surfaces were investigated with numerical techniques regarding their potential to reduce sputtering by ion bombardment. We simulated a large number of different configurations with the SPRAY sputtering code to identify an optimal geometry. For the test case of 2 keV ${\mathrm{Ar}}^{+}$ irradiation, a specific configuration was found which led to a significant sputter yield reduction for all studied ion incidence angles. For example, reductions by $\ensuremath{\sim}80$% in comparison to the sputter yield values for a flat tungsten surface were observed during irradiation along the surface normal. These properties appear beneficial for application on first wall materials in nuclear fusion devices. The optimized surface was further investigated with the molecular dynamics code PARCAS and the binary-collision-approximation code SDTrimSP-3D, which supported the choice of this configuration. Furthermore, dynamic erosion simulations using SDTrimSP-3D were conducted, which predict a relatively long-lasting persistence of the sputter yield reduction if the structure is exposed to higher fluences.

10.1103/physrevmaterials.7.065406

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Citations (3)

Simulations of cementite: An analytical potential for the Fe-C system

Physical Review B (2009)

K. O. E. Henriksson K. Nordlund

An analytical bond-order interatomic potential has been developed for the iron-carbon system for use in molecular-dynamics and Monte Carlo simulations. The potential has been successfully fitted to cementite and H\"agg carbide, which are most important crystalline polytypes among the many known metastable iron carbide phases. Predicted properties of other carbides and the simplest point defects are in good to reasonable agreement with available data from experiments and density-functional theory calculations. The potential correctly describes melting and recrystallization of cementite, making it useful for simulation of steels. We show that they correctly describe the metastability of cementite and can be used to model carbide growth and dissolution.

Metastability

Embedded atom model

Recrystallization (geology)

10.1103/physrevb.79.144107

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Citations (79)

Molekydynamiska simuleringar av strålningsskador i FeCr

C. Björkas K. Vörtler K. Nordlund D Terentyev L Malerba

Source

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Citations (0)

Effect of cascade overlap and C15 clusters on the damage evolution in Fe: An OKMC study

Materialia (2022)

Amin Esfandiarpour Jesper Byggmästar J.P. Balbuena M.J. Caturla K. Nordlund

Laves phase

Kinetic Monte Carlo

radiation damage

10.1016/j.mtla.2022.101344

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Citations (4)

Simple analytical model of nanocluster coalescence for porous thin film design

Modelling and Simulation in Materials Science and Engineering (2014)

Panagiotis Grammatikopoulos Evropi Toulkeridou K. Nordlund Mukhles Sowwan

We propose an approach to coalescence studies that encompasses the random nature of nanoparticle deposition, which results in a statistical cancellation of individual sintering mechanisms. We present a rigorous, yet simple and intuitive, analytical method that describes the average coalescence behaviour of nanoparticles, regardless of constituent element or crystallinity, emphasizing only the predominant coalescence dependencies on temperature and size-dependent nanoparticle melting points. We assessed our model using molecular dynamics (MD) computer simulations of dissimilar systems, and found remarkable agreement between its predictions and the MD results. Its simplicity makes our model a suitable starting point for the development of a meso-scale simulation technique that can describe the growth of porous films and allow for their bespoke design.

Coalescence (physics)

Bespoke

10.1088/0965-0393/23/1/015008

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Citations (15)

The EU programme for modelling radiation effects in fusion reactor materials: An overview of recent advances and future goals

Journal of Nuclear Materials (2008)

S. L. Dudarev Jean-Louis Boutard R. Lässer M.J. Caturla P. M. Derlet

Embrittlement

Fusion power

Hardening (computing)

10.1016/j.jnucmat.2008.12.301

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Citations (83)