People

Materials Science simulations
	Person	Position	Scientic interests
	Prof. Kai Nordlund	Team leader	Computational materials physics
	Dr Antti Kuronen1	University lecturer	Computational materials physics
	Dr Krister Henriksson	Docent, senior scientist	Fusion reactor materials; potential development
	Dr Juha Samela	Postdoc (on free time)	Cratering and sputtering
	Dr Carolina Björkas	Postdoc	Potential development, fusion reactor materials
	Dr. Lotta Mether	Postdoc	Molecule deposition
	Jussi Polvi	PhD student	Processing of cellulose
	Ville Jansson	PhD student (working at SCK-CEN Belgium)	Fusion reactor materials
	Ane Lasa	PhD student	Fusion reactor materials
	Andrea Meinander	PhD student	Fusion reactor materials
	Mohammad Wali Ullah	PhD student	GaN and ZnO
	Andrey Ilinov	PhD student	Mechanical properties of nanostructures
	Laura Bukonte	PhD student	Fusion reactor materials
	Daniel Landau	Part-time student	Code development, cratering
	Wei Ren	Summer student	Nanowires
	Matias Vestberg	Summer student	Surface nanostructures
	Sara Tähtinen	Summer student	Plasma-material interactions
Nanocarbon simulations
	Dr Arkady Krasheninnikov	Docent, senior scientist	Carbon nanostructures
	Dr Jani Kotakoski	Docent, senior scientist	Carbon and BN nanosystems, nitrogen under pressure
	Dr Hannu-Pekka Komsa	Postdoc	Carbon and BN nanosystems
	Harriet Åhlgren	Part-time student	Carbon nanostructures
HIP theory project
	Dr Flyura Djurabekova	Docent, senior scientist, Group leader (HIP)	Surface damage in particle accelerator materials; Nanoclusters in solids
	Dr Olli Pakarinen	Postdoc	Nanoclusters in solids; ion tracks
	Dr. Eero Holmström	Postdoc	Quantum molecular dynamics; damage in Si detectors
	Aarne Pohjonen	PhD student	Particle physics materials
	Stefan Parviainen	PhD student	Particle physics materials
	Avaz Ruzibaev	PhD student	Particle physics materials
	Marie Backman	PhD student	Silicon nanocrystals
	Konstantin Avchachov	PhD student	Damage in silica
	Aleksi Leino	PhD student	Nanocrystals in silica
	Fredric Granberg	Part-time student	Nanowires
	Riikka Ruuth	Summer student	Surface damage
	Juho Arjoranta	Summer student	Surface properties
	Johann Muszynski	Summer student	Dislocations near surfaces
Graduated members
	Person	Left group	Interests while in group
	Dr Jura Tarus	2004	Radiation effects in semiconductors
	Dr. Jussi Sillanpää	2000	Stopping power modelling
	Dr Emppu Salonen	2003	Fusion reactor materials; carbon nanotubes
	Dr Jarkko Peltola	2003	Stopping power of ions and clusters
	Dr Janne Nord	2004	Irradiation effects in compound semiconductors; potential development
	Dr Jonas Frantz	2004	Nanoclusters
	Dr Petra Träskelin	2007	Surface reactions in fusion reactor divertors
	Dr Tommi Järvi	2009	Nanocluster deposition
	Dr Kristoffer Meinander	2009	Nanoclusters (both simulation and experiment)
	Dr Niklas Juslin	2010	Potential development, fusion reactor materials
	Dr. Antti Tolvanen	2010	Ion irradiation of carbon nanotubes
	Dr. Helga Timko	2011	Particle accelerator materials
	Dr. Ari Harjunmaa	2011	Nanoclusters
	Dr. Katharina Vörtler	2011	Radiation effects in W, Fe and FeCr

Summary of main projects

The projects are listed in reverse chronological from when they were started.

	Topic: Processing of organic materials Duration: 2007- People: Jussi Polvi, Petri Luukkonen, Tommi Järvi, Kai Nordlund Description: Organic polymeric materials such as polyethylene and cellulose can be processed with irradiation and supercritical fluids. Using reactive interatomic potentials like ReaxFF as well as molecular mechanics codes like Gromacs, we are examining how the properties of polymeric materials can be modified.
	Topic: Particle physics materials Duration: 2007- People: Flyura Djurabekova, Eero Holmström, Helga Timko, Stefan Parviainen, Aarne Pohjonen, Avaz Ruzibaev, Juha Samela, Kai Nordlund Description: The development of particle physics requires accelerators which produce particle beams with increasingly high energy and intensity. This leads unavoidably to increasingly large demands on the materials surrounding the particle beam. In our HIP theory programme activity we examine the fundamental mechanisms by which the damage in accelerator components form, with the aim to use the increased understanding to design materials and components which withstand the damage optimally well. More information: HIP theory project pages
	Topic: Embedded nanoclusters Duration: 2007- People: Flyura Djurabekova, Marie Backman, Kai Nordlund, Olli Pakarinen, Aleksi Leino Description: Small nanocrystals dispersed in dielectric matrices are prospective composite materials for Si-based optoelectronics and solid-state memory applications. Using molecular dynamics methods, we are constructing atomistic models of nanoclusters in solids, and then examining their further processing by laser annealing or ion irradiation. We also examine the radiation hardness of the silica matrix itself both under keV and MeV swift heavy ion irradiation. Key references: F. Djurabekova and K. Nordlund, Phys. Rev. B 77 (2008) 115325; P. Kluth et al, Phys. Rev. Lett. 101, 175503 (2008) M. Backman, F. Djurabekova et al, Phys. Rev. B 80, 144109 (2009).
	Topic: Nanoindentation Duration: 2006- People: Heikki Ristolainen, Antti Kuronen, Darek Chrobak (TKK), Roman Nowak (TKK), Kai Nordlund Description: Nanoindentation, i.e. pressing a nanoscale needle against surfaces, enables analysis and modification of material surfaces on the atomistic scale. We are using computer simulation to examine nanoindentation, especially focusing on the mechanisms of materials modification. Key references: D. Chrobak, K. Nordlund, and R. Nowak, Phys. Rev. Lett. 98 (2007) 045502.
	Topic: Carbon nanostructures Duration: 2000- People: Arkady Krasheninnikov, Kai Nordlund, Jani Kotakoski, Antti Tolvanen Description: Carbon nanostructures are in many ways very exciting materials. From a basic physics viewpoint they are interesting in that they essentially provide a completely one-dimensional electron system. The very high elastic strength and interesting electronic and optical properties also show great promise for practical application. We are examining how defects introduced by ion irradiation could be used to modify the atomic structure, and hence mechanical and electronic properties of nanostructures. Key references: Krasheninnikov, Nordlund, Sirviö, Salonen, Keinonen, Phys. Rev. B 63 (2001) 245450 Krasheninnikov, Nordlund, Keinonen, Phys. Rev. B 65 (2002) 164523 Åström, Krasheninnikov, Nordlund, Phys. Rev. Lett. 93 (2004) 215503 Sun, Banhart, Krasheninnikov, Rodriguez-Manzo, Ajayan, Science 312 (2006) 1199 L. Sun, A. V. Krasheninnikov, T. Ahlgren, K. Nordlund, and F. Banhart, Phys. Rev. Lett. 101, 156101 (2008); J. A. Rodr'iguez-Manzo, I. Janowska, C. Pham-Huu, A. Tolvanen, A. V. Krasheninnikov, K. Nordlund, and F. Banhart, Small (2009)
	Topic: Nanoclusters Duration: 1999- People: Kristoffer Meinander, Tommi Järvi, Eero Kesälä, Flyura Djurabekova, Antti Kuronen, Kai Nordlund Description: Nanoclusters, i.e. agglomerates of typically 10 - 100000 atoms, show great promise for enabling the manufacturing of new kinds of materials. We are examining the basic processes occuring when nanoclusters form, are deposited on surfaces, and the properties of nanoclusters embedded in a bulk, Key references: Zimmermann, Yeadon, Ghaly, Nordlund, Gibson, Averback, Herr, Samwer, Phys. Rev. Lett. 83 (1999) 1163. Frantz, Nordlund, Phys. Rev. B. 67, 075415 (2002) Peltola, Nordlund, Phys. Rev. B 68, 035419 (2003) Frantz, Nordlund, Jahma, Koponen, Phys. Rev. B 71 (2004) 075411 K. Meinander, T. T. Järvi, and K. Nordlund, Appl. Phys. Lett. 89 (2006) 253109 E. Kesälä, A. Kuronen, and K. Nordlund, Phys. Rev. B 75, 174121 (2007).
	Topic: Fusion reactor materials Duration: 1998- People: Carolina Björkas, Niklas Juslin, Katharina Vörtler, Kai Nordlund, Ane Lasa, Andrea Meinander Description: One of the main remaining challenges to developing a commercially viable fusion reactor is finding a material which can withstand the enormous radiation load in the divertor part of the reactor. To this end, we are examining the radiation tolerance of both carbon- and heavy-metal-based candidate materials for divertors. We are also studying the radiation damage tolerance of FeCr alloys as model materials for special reactor material steels. Key references: Salonen, Nordlund, Tarus, Ahlgren, Keinonen, Wu, Phys. Rev. B 60 (1999) R14005. Salonen, Nordlund, Keinonen, Wu, Europhys. Lett. 52 (2000) 504. Salonen, Nordlund, Keinonen, Wu, Phys. Rev. B 63 (2001) 195415. Träskelin, Salonen, Nordlund, Krasheninnikov, Keinonen, J. Appl. Phys. 93 1826 (2003) Henriksson, Nordlund, Krasheninnikov, Keinonen, Appl. Phys. Lett. 87 (2005) 163113 Björkas, Vörtler, Nordlund, Phys. Rev. B (Rapid comm.) 74 (2006) 140103.
	Topic: Interstitials in solid and liquid metals Duration: 1997- People: Kai Nordlund, Yinon Ashkenazy (UIUC), Bob Averback (UIUC) Description: In 1992 A. V. Granato [Phys. Rev. Lett. 68, 974] published a model which predicts that interstitials have surprisingly high concentrations in metals close to the melting point, and that this has a close connection with the properties of liquids. Using extensive MD simulations we have observed the spontaneous formation of Frenkel pairs in metals, and from this information deduced the interstitial formation entropy and enthalpy. The high value we find strongly supports the Granato model. We have also showed that the strings in liquids (as described by Schober, Glotzer and others) can be considered to be manifestations of the interstitials in the Granato model. Key references: Nordlund, Averback, Phys.Rev. Lett. 80 (1998) 4201 K. Nordlund, Y. Ashkenazy, R. S. Averback and A. V. Granato, Europhys. Lett. 71 (2005) 625.
	Topic: Diffuse x-ray scattering Duration: 1996- People: Kai Nordlund, Eero Holmström, Hartmut Metzger (Grenoble) Description: One of the very few experimental tools which directly probe the atomic structure of defects in solids is diffuse x-ray scattering (DXS). Although it in principle is a powerful tool in that it can detect the symmetry of the strain field of any defect, its use has been somewhat hampered by the difficulty of interpreting the signal coming from any but the most simple defectt types. To this end, we have developed an atomistic simulation method which can predict the DXS from any defect configuration in any crystal. In combination with experiments we have used the method to analyze the structure and stability of the interstitial and stacking faults in Si. Key references: Nordlund, Partyka, Averback, Robinson, Ehrhart, J. Appl. Phys. 88 (2000) 2278. Partyka, Zhong, Nordlund, Averback, Robinson, Ehrhart, Phys. Rev. B 64 (2001) 235207 Nordlund, Beck, Metzger, Patel, Appl. Phys. Lett. 76 (2000) 846 Nordlund, J. Appl. Phys. 91, 2978 (2002). M.-I. Richard, T. H. Metzger, V. Holy, and K. Nordlund, Phys. Rev. Lett. 99 (2007) 225504
	Topic: Semiconductors Duration: 1996- People: Eero Holmström, Antti Kuronen, Kai Nordlund, Karsten Albe (TU Darmstadt) Description: Ion implantation is widely used in semiconductor manufacturing. We are examining the basic physics of how damage is produced and can be annealed in Si, Ge and compound semiconductors. An important part of this work is development interatomic potential models for compound semiconductors such as GaAs and GaN suitable for simulations of nonequilibrium phenomena. Key references: Nordlund, Ghaly, Averback, Caturla, Diaz de la Rubia, Tarus, Phys. Rev. B 57 (1998) 7556. Kyuno, Cahill, Averback, Tarus, Nordlund, Phys. Rev. Lett. 83 (1999) 4788. Nordlund, Peltola, Nord, Keinonen, Averback, J. Appl. Phys. 90 (2001) 1710. Nordlund, Peltola, Nord, Keinonen, Averback, J. Appl. Phys. 90, 1710 (2001) Nord, Nordlund, Keinonen, Phys. Rev. B 65, 165329 (2002) Nord, Albe, Erhart, Nordlund, J. Phys: Cond. Matter 15, 5649 (2003). Nord, Nordlund, Keinonen, Phys. Rev. B 68, 184104 (2003). Look, Farlow, Reunchan, Limpijumnong, Zhang and Nordlund, Phys. Rev. Lett. 95 (2005) 225502
	Topic: Radiation damage in metals Duration: 1996- People: Kai Nordlund, Krister Henriksson, Jarkko Peltola, Bob Averback (UIUC) Description: We are examining the mechanisms by which ions and neutrons produce damage in metals. This is an old and broad topic, and our studies have focused mainly on two aspects; elucidating the role of surfaces on damage production, and examining ion beam mixing effects. We have also looked at cluster emission from heat spikes, on cluster stopping effects, and ordering/disordering in irradiated metal alloys, and most recently have started developing potentials and studying cascades in FeCr as a model material for high-chromium steels. More information: Animations; even more animations Key references: Nordlund, Zhong, Wei, Averback: Phys. Rev. B. 57 (1998) 13965 Nordlund, Keinonen, Ghaly, Averback: Nature 398 (1999) 49 Nordlund and Gao, Appl. Phys. Lett. 74 (1999) 2720 Bringa, Nordlund, Keinonen: Phys. Rev. B 64 (2001) 235426 Nordlund, Henriksson, Keinonen, Appl. Phys. Lett.79 (2001) 3624 Olsson, Wallenius, Domain, Nordlund, Malerba, Phys. Rev. B 72 (2005) 214119
	Topic: Graphite and graphene surface defects Duration: 1994-1996, 2001- People: Arkady Krasheninnikov, Emppu Salonen, Kai Nordlund Description: In studying ion irradiation of graphite surfaces back around 1995, we found other things a new defect type where an extra atom has entered the graphite surface layer, forming a stable adatom like defect. This "D3" defect may explain some of the experimentally seen hillocks on graphite. After a hiatus of many years, we are now examining the energetics and mobility of this and other defects in graphite and graphene in greater detail More information: Animations Key references: Nordlund, Mattila, Keinonen: Phys. Rev. Lett. 77 (1996) 699 Lehtinen, Foster, Ayuela, Krasheninnikov, Nordlund, and Nieminen, Phys. Rev. Lett. 91, 017202 (2003) A. V. Krasheninnikov, P.O. Lehtinen, A.S. Foster, P. Pyykko, and R. M. Nieminen, Phys. Rev. Lett. 102 (2009) 126807.
	Topic: Ion depth distributions, stopping powers Duration: 1992-2003 People: Jarkko Peltola, Jussi Sillanpää, Kai Nordlund, Martti Puska (HUT) Description: We have developed the first widely applicable ion range calculation code fully based on molecular dynamics algorithms "MDRANGE". At low ion energies (less than 100 eV/amu or so) it is more accurate than any BCA method. The standard version can use any non-local electronic stopping such as the ZBL model. Recently we have developed physically well motivated local electronic stopping models for channeling directions in semiconductors. The active development of MDRANGE has stopped for now, but we continue maintaining and distributing the code and using it in applications. More information: Range calculations ; MDRANGE Key references: Nordlund, Comput. Mater. Sci. 448 (1995) 448 Sillanpää et al., Phys. Rev. B 63 (2000) 134113 Peltola, Nordlund, Keinonen, Nucl. Instr. Meth. Phys. Res. B 212, 118 (2003)
	Topic: Gamma-ray induced Doppler Broadening Duration: 1989-1994 People: Antti Kuronen, Juhani Keinonen, Kai Nordlund Description: When a sample is irradiated with thermal neutrons, some nuclei capture a neutron, go into an exited state and decay from this state by emitting gamma-ray cascades. When a nucleus emits a gamma quantum it gets kicked out of its lattice position, whence the second gamma particle emitted will have a Doppler-broadened energy. We developed a molecular dynamics method to study this "GRID" process, enabling analysis of both nuclear lifetimes and solid state interatomic potentials. Key references: Keinonen, Kuronen, Tikkanen, Borner, Jolie, Ulbig, Kessler, Nieminen, Puska, Seitsonen, Phys. Rev. Lett. 67 (1991) 3692 Raman, Jurney, Warner, Kuronen, Keinonen, Nordlund, Millener, Phys. Rev. C. 50 (1994) 682

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