Thesis advisor: David A. Broido / A theory is presented for describing the lattice thermal conductivities of graphene and single-walled carbon nanotubes. A phonon Boltzmann transport equation approach is employed to describe anharmonic phonon-phonon, crystal boundary, and isotopic impurity scattering. Full quantum mechanical phonon scattering is employed and an exact solution for the linearized Boltzmann transport equation is determined for each system without use of common relaxation time and long-wavelength approximations. The failures of these approximations in describing the thermal transport properties of nanotubes is discussed. An efficient symmetry based dynamical scheme is developed for carbon nanotubes and selection rules for phonon-phonon scattering in both graphene and nanotubes are introduced. The selection rule for scattering in single-walled carbon nanotubes allows for calculations of the thermal conductivities of large-diameter and chiral nanotubes that could not be previously studied due to computational limitations. Also due to this selection rule, no acoustic-only umklapp scattering can occur, thus, acoustic-optic scattering must be included in order to have thermal resistance from three-phonon processes. The graphene selection rule severely restricts phonon-phonon scattering of out-of-plane modes. This restriction leads to large contributions to the total thermal conductivity of graphene from the acoustic, out-of-plane modes which have been previously neglected. Empirical potentials used to model interactions in carbon-based materials are optimized to better describe the lattice dynamics of graphene-derived systems. These potentials are then used to generate the interatomic force constants needed to make calculations of the thermal conductivities of graphene and carbon nanotubes. Calculations of the thermal conductivities of single-walled carbon nanotubes and graphene for different temperatures and lengths are presented. The thermal conductivities of SWCNTs saturate in the diffusive regime when the effects of higher-order scattering processes are estimated and correctly reproduce the ballistic limit for short-length nanotubes at low temperatures. The effects of isotopic impurity scattering on the thermal conductivities of graphene and SWCNTs are explored. Isotopic impurities have little effect in the low (high) temperature regime where boundary (umklapp) scattering dominates the behavior of the thermal conductivities. In the intermediate temperature regime, modest reductions in the thermal conductivities, 15-20%, occur due to impurities. The thermal conductivities of a wide-range of SWCNTs are explored. The thermal conductivities of successively larger-diameter, one-dimensional nanotubes approach the thermal conductivity of two-dimensional graphene. / Thesis (PhD) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

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Title: Molecular simulations of ice nucleation Author: Eva Pluhařová Department: Department of Physical and Macromolecular Chemistry Faculty of Science UK Advisor: doc. Mgr. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's e-mail address: pavel.jungwirth@uochb.cas.cz Abstract: By means of molecular dynamics simulations we have systematically investigated homogeneous ice nucleation in neat and surface contaminated water. As models of the adsorbates we have assumed pentanol and pentanoic acid. In neat water nucleation preferentially starts in the subsurface region, which accommodates better than the bulk the volume increase associated with freezing. Homogeneous ice nucleation is affected more by alcohol than by acid. Water slabs covered by a disordered layer of pentanol exhibit negligible preference for subsurface nucleation and longer nucleation times in comparison with neat water, while nucleation times are almost unaffected by the presence of pentanoic acid and the subsurface preference is only slightly decreased. We tried to rationalize the differences between the effects of different compounds by their ability to orient water molecules and to change their mobility. The fact that adsorbates differ in the influence on homogeneous ice nucleation has important implications for the microphysics of...

In recent years, the design, fabrication, and control of robotic systems inspired by biology has gained renewed attention due to the potential improvements in efficiency, maneuverability, and adaptability with which animals interact with their environments. Motion studies of biological systems such as humans, fish, insects, birds and bats are often used as a basis for robotic system design. Often, these studies are conducted by recording natural motions of the system of interest using a few high-resolution, high-speed cameras. Such equipment enables the use of standard methods for corresponding features and producing three-dimensional reconstructions of motion. These studies are then interpreted by a designer for kinematic, dynamic, and control systems design of a robotic system. This methodology generates impressive robotic systems which imitate their biological counter parts. However, the equipment used to study motion is expensive and designer interpretation of kinematics data requires substantial time and talent, can be difficult to identify correctly, and often yields kinematic inconsistencies between the robot and biology. To remedy these issues, this dissertation leverages the use of low-cost, low-speed, low-resolution cameras for tracking bat flight and presents a methodology for automatically learning physical geometry which restricts robotic joints to a motion submanifold identified from motion capture data. To this end, we present a spatially recursive state estimator which incorporates inboard state correction for producing accurate state estimates of bat flight. Using these state estimates, we construct a Gaussian process dynamic model (GPDM) of bat flight which is the first nonlinear dimensionality reduction of flapping flight in bats. Additionally, we formulate a novel method for learning robotic joint geometry directly from the experimental observations. To do this, we leverage recent developments in learning theory which derive analytical-empirical potential energy fields for identifying an underlying motion submanifold. We use these energy fields to optimize a compliant structure around a single degree-of-freedom elbow joint and to design rigid structures around spherical joints for an entire bat wing. Validation experiments show that the learned joint geometry restricts the motion of the joints to those observed during experiment. / Ph. D. / In recent years, robots modeled after biological systems have become increasingly prevalent. Such robots are often designed based on motion capture experiments of the animal they aim to imitate. The motion studies are typically conducted using commercial motion capture systems such as ViconTM or OptiTrackTM or a few high-speed, high-resolution cameras such as those marketed by PhotronTM or PhantomTM. These systems allow for automated processing of video sequences into three-dimensional reconstructions of the biological motion using standard image processing and state estimation techniques. The motion data is then used to drive robotic system designs such as the SonyTM AiboTM dog and the Boston Dynamics Atlas humanoid robot. While the motion capture data forms a basis for these impressive robots, the progression from data to robotic system is neither algorithmic nor rigorous and requires substantial interpretation by a human. In contrast, this dissertation presents a novel experimental and computational framework which uses low-speed, low-resolution cameras for capturing the complex motion of bats in flight and introduces a methodology which uses the motion capture data to directly design geometry which restricts the motion of joints to the motions observed in experiment. The advantage of our method is that the designer only needs to specify a general joint geometry such as a ball or pin joint, and geometry which restricts the motion is automatically identified. To do this, we learn an energy field over the set of kinematic configurations observed during experiment. This energy field “pushes” system trajectories towards those experimentally observed trajectories. We then learn compliant or rigid geometry which approximates this energy field to physically restrict the range of motion of the joint. We validate our method by fabricating joint geometry designed using both these approaches and present experiments which confirm that the reachable set of the joint is approximately the same as the set of configurations observed during experiments.

Les matériaux composants les réacteurs nucléaires subissent des conditions d’irradiationsévères, donnant lieu à des modifications de leurs propriétés mécaniques. Le vieillissement de cesmatériaux soulève des questions aussi importantes que celles liées à la sécurité des centrales existantes etaux futurs réacteurs à fission et à fusion. Dans plusieurs situations les matériaux de structure cristallinecubique centrée CC sont utilisés ayant pour base le fer, le tungstène, le vanadium et le tantale. Lescollisions entre les particules irradiantes et les atomes constituants les matériaux engendrent des défautsponctuels dont la migration mène à la formation d’amas responsables du vieillissement. Dans cette thèsenous avons étudié les propriétés énergétiques des défauts ponctuels dans les métaux CC citésprécédemment à l’échelle atomique. La modélisation des défauts ponctuels à l’échelle atomique peut êtreréalisée avec différentes méthodes se différenciant uniquement par la qualité de la description del’interaction entre atomes. Les études utilisant des interactions atomiques exactes, type ab initio,nécessitent des calculs lourds rendant impossible l’étude directe des amas de grandes tailles. Avec lamodélisation des interactions atomiques via les potentiels semi-empiriques on réduit la fiabilité et lecaractère prédictif du calcul. Ceux-ci permettent toutefois de réaliser une étude des amas en fonction deleur taille. Dans cette thèse nous avons développé un modèle énergétique original pour les boucles dedislocation ainsi que pour les amas interstitiels tridimensionnels de type C15. Le modèle obtenu est sanslimite de taille et peut être paramétré entièrement par les calculs ab initio. Afin de tester sa robustessepour les grandes tailles d’amas nous avons également paramétré ce modèle par rapport à des calculs enpotentiels semi-empiriques et comparé les prédictions du modèle aux simulations atomiques. Grâce ànotre développement nous avons pu déterminer : (i) la stabilité relative des boucles de dislocationd’interstitiels d’après leur vecteur de Burgers. (ii) La stabilité des amas C15 par rapport aux amas de typeboucle. Nous avons montré que les amas de type C15 étaient plus stables lorsqu’ils impliquent moins de41 interstitiels dans le fer. (iii) Dans le Ta nous avons pu mettre en évidence la même stabilité jusqu’à 20interstitiels. Les expériences dans le fer irradié montrent qu’en fonction de la température d’irradiation, ilse forme des boucles de dislocation très mobiles de vecteur de Burgers ½<111> ou immobiles ayant unvecteur de Burgers <100>. Les mécanismes de formation sous irradiation en fonction de la température,des amas de type <100> étaient une question restée sans explication théorique depuis 50 ans. Dans cettethèse, grâce à la précision de notre modèle énergétique, nous avons pu tester plusieurs théories.Notamment nous avons montré que les amas C15 constituent un catalyseur dans la formation des boucles<100>. Les clusters C15 peuvent se former, par germination, directement dans le processus d’irradiation.Ces clusters sont immobiles et peuvent croitre. A partir d’une certaine taille les amas C15 se dissocienten boucles ½ <111> ou <100>. Nous avons étendu notre modèle au calcul d’énergie libre de formationdes défauts permettant ainsi des prédictions à température finie que nous avons comparées auxsimulations atomiques. Les lois établies dans cette thèse en utilisant notre modéle pour calculer l’énergielibre de formation en fonctions de la taille des amas, ont été ensuite utilisées dans une simulation dedynamique d’amas. Nous avons ainsi pu prédire avec un très bon accord expérience-théorie laconcentration des amas d’interstitiels en fonction de leurs tailles au cours du murissement d’Oswald postirradiationdans un échantillon de Fer sous atmosphère d’Hélium. Le succès d’une telle approche nouspermet d’espérer étendre ce type d’étude à des matériaux plus complexes. / The structural materials in nuclear reactors are subjected to severe irradiation conditions,leading to changes in their mechanical properties. The aging of these materials raises important issuessuch as those related to the safety of existing plants and future reactors. In many cases, materials withbody-centered cubic bcc crystal structure are used with iron, tungsten, vanadium and tantalum as basemetal. Collisions between irradiating particles and atoms constituting materials generate point defectswhose migration leads to the formation of clusters responsible for aging. In this thesis, we studied theenergetic properties of point defects in the bcc metals mentioned above at the atomic scale. Modelingpoint defects at the atomic scale can be achieved with different methods that differ only in the quality ofthe description of the interaction between atoms. Studies using accurate atomic interactions such ab initiocalculations are computationally costly making it impossible to directly study clusters of large sizes. Themodeling of atomic interactions using semi-empirical potentials reduces the reliability of predictivecalculations but allow calculations for large-sized clusters. In this thesis we have developed a uniqueenergy model for dislocation loops as well as for three-dimensional interstitial cluster of type C15. Theresulting model has no size limit and can be set entirely by ab initio calculations. To test its robustness forlarge sizes of clusters we also set this model with semi-empirical potentials calculations and comparedthe predictions of the model to atomic simulations. With our development we have determined: (i) Therelative stability of interstitial dislocation loops according to their Burgers vectors. (ii) The stability of theclusters C15 compared to the type of cluster loop. We showed that the C15 type clusters are more stablewhen they involve less than 41 interstitials in iron. (iii) In Ta we were able to show the same stability till20 interstitials. The experiments involving iron show that depending on the irradiation temperature,highly mobile dislocation loops of Burgers vector ½ <111> or loops with Burgers vector <100> areformed. Considering formation mechanisms under irradiation as a function of temperature, formation ofthe <100>-type clusters lacked an acceptable theoretical explanation for about 50 years. In this thesis, theaccuracy of our energy model enabled validation of several theories proposed in the last 50 years. Inparticular we have shown that the formation of loops <100> at high temperatures can be formed fromC15 clusters which may be created directly in the irradiation process. These clusters are immobile andcan grow. Beyond a certain size, the C15 clusters dissociate into loops ½ <111> or <100>. We haveextended our model to free energy calculation of defect formation allowing for finite temperaturepredictions which is further compared to atomic simulations. The laws established in this thesis using ourmodel to calculate the free energy of formation of the cluster size functions were then used in a clusterdynamics simulation. On comparison with experiments involving post-irradiation Oswald ripening in asample of iron exposed to an atmosphere of helium, our energy model showed significant improvementsover older energy laws, such as the capillary law widely-used in multiscale computation cluster dynamicsor Monte Carlo kinetics. We conclude that the new laws established from our calculations are essential topredict the concentration of dislocation loop under irradiation, depending on their sizes. The success ofsuch an approach encourages extension of a similar study in more complex materials.

Title: Computer modeling of ion protein interactions: Allosteric effects of phenolic ligands and ions on insulin hexamer structure Author: Vladimír Palivec Department: Department of Physical and Macromolecular Chemistry Faculty of Science UK Advisor: prof. RNDr. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's email address: pavel.jungwirth@uochb.cas.cz Abstract: Insulin hexamer is an allosteric protein capable of undergoing conformational changes between three states: T6, T3R3, and R6. Transitions between them, as well as the formation of insulin hexamers, are mediated through binding of phenolic ligands or ions. This thesis presents a molecular dynamics study of allosteric behavior of insulin using empirical force fields. Two effects are closely inspected - cation (Zn2+ , Ca2+ , K+ , and Na+ ) binding to the insulin hexamers and a possible binding of two neurotransmitters - dopamine and serotonin to the phenolic pocket. The results show that high charge density cations (Zn2+ and Ca2+ ) are mostly localized in the B13 glutamate cavity, slow- down diffusion, while preventing other cations from entering. In contrast, low charge density cations (Na+ and K+ ) do not have this effect. Concerning neurotransmitters, dopamine does not bind to the phenolic pocket whereas serotonin binds in a similar way like...

The presence of the ordered $\gamma^{\prime}$ phase ($\text{Ni}_{3}\text{Al}$) in Ni-base superalloys is fundamental to the performance of engineering components such as turbine disks and blades which operate at high temperatures and loads. Hence for these alloys it is important to optimize their microstructure and phase composition. This is typically done by varying their chemistry and heat treatment to achieve an appropriate balance between $\gamma^{\prime}$ content and other constituents such as carbides, borides, oxides and topologically close packed phases. In this work we have set out to investigate the onset of $\gamma^{\prime}$ ordering in Ni-Al single crystals and in Ni-Al bicrystals containing coincidence site lattice grain boundaries (GBs) and we do this at high temperatures, which are representative of typical heat treatment schedules including quenching and annealing. For this we use the atomistic simulation methods of molecular dynamics (MD) and density functional theory (DFT). In the first part of this work we develop robust Bayesian classifiers to identify the $\gamma^{\prime}$ phase in large scale simulation boxes at high temperatures around 1500 K. We observe significant \gamma^{\prime} ordering in the simulations in the form of clusters of $\gamma^{\prime}$-like ordered atoms embedded in a $\gamma$ host solid solution and this happens within 100 ns. Single crystals are found to exhibit the expected homogeneous ordering with slight indications of chemical composition change and a positive correlation between the Al concentration and the concentration of $\gamma^{\prime}$ phase. In general, the ordering is found to take place faster in systems with GBs and preferentially adjacent to the GBs. The sole exception to this is the $\Sigma3 \left(111\right)$ tilt GB, which is a coherent twin. An analysis of the ensemble and time lag average displacements of the GBs reveals mostly `anomalous diffusion' behaviour. Increasing the Al content from pure Ni to Ni 20 at.% Al was found to either consistently increase or decrease the mobility of the GB as seen from the changing slope of the time lag displacement average. The movement of the GB can then be characterized as either `super' or `sub-diffusive' and is interpreted in terms of diffusion induced grain boundary migration, which is posited as a possible precursor to the appearance of serrated edge grain boundaries. In the second part of this work we develop a method for the training of empirical interatomic potentials to capture more elements in the alloy system. We focus on the embedded atom method (EAM) and use the Ni-Al system as a test case. Recently, empirical potentials have been developed based on results from DFT which utilize energies and forces, but neglect the electron densities, which are also available. Noting the importance of electron densities, we propose a route to include them into the training of EAM-type potentials via Bayesian linear regression. Electron density models obtained for structures with a range of bonding types are shown to accurately reproduce the electron densities from DFT. Also, the resulting empirical potentials accurately reproduce DFT energies and forces of all the phases considered within the Ni-Al system. Properties not included in the training process, such as stacking fault energies, are sometimes not reproduced with the desired accuracy and the reasons for this are discussed. General regression issues, known to the machine learning community, are identified as the main difficulty facing further development of empirical potentials using this approach.

Ziel der Arbeit ist die theoretische Analyse von Kohlenstoff-Clustern der Größe 100 - 500 Atome. Die experimentellen Beobachtungen sind bei dieser geringen Anzahl der Atome schwierig. Anderseits sind Kenntnisse über solche Cluster sehr wichtig, z.B. für die Keimbildung von Diamant auf Substraten, oder für die Kohlenstoff-Nanotechnologie (Fullerene, Nanotubes), oder für strukturelle Defekte in Kohlenstoff-Systemen. Es wurden gekrümmte Grenzflächen im Diamant simuliert. Zuerst mit einem empirischen Potential. Es wurde danach eine Methode entwickelt, bei der die schwach gestörten Gebiete einem empirischen Potential gehorchen, und die stark gestörten Gebiete, wo eine genaue Berechnung erforderlich ist, durch eine quantenmechanische Näherung beschrieben wurden. Somit kann man mit guter Genauigkeit große Systeme, bestehend aus einigen 10 (hoch)4 Atomen, simulieren, bei denen nur lokal quantenmechanische Methoden erforderlich sind. Mit diesem Hybrid-Code wurden weiterhin Diamantkeime auf Silizium gerechnet. Es wurden Aussagen bezüglich der Stabilität des Diamants auf dem Siliziumsubstrat, der kritischen Keimgröße, der Änderungen, die der Keim erfährt, gemacht. Ein anderes Gebiet ist die molekulardynamische Simulation bezüglich der Stabilität und des Transformationsverhaltens von Kohlenstoff-Nanoteilchen. Es wurden als »Rohstoffe» sowohl Diamant- und Graphitkristalle sphärischer, ellipsoidischer oder quadratischer Form benutzt, als auch amorpher Kohlenstoff. Es wurde demonstriert, daß sich Diamant unter höherer Temperatur und Bestrahlung in Kohlenstoffzwiebeln transformiert. Es wurde der innere Kern, bestehend aus zwei Schalen, der Kohlenstoffzwiebel simuliert. Es wurde, nach meinem Wissen, zum ersten Mal gezeigt, daß zwischen den Schalen der Kohlenstoffzwiebel Quer-Verbindungen (cross-links) existieren. Diese waren von den Experimentatoren vermutet worden. Sie bilden die Initiatoren der Diamantkeime der Kohlenstoffzwiebel bei ihrer ohne äußeren Druck möglichen Transformation in Diamant. Die Zentren der Kohlenstoffzwiebeln befinden sich bereits in der Entstehung der Zwiebel unter einem Selbstdruck. Bei den größeren Kohlenstoffzwiebeln beträgt der experimentell bestimmte Abstand zwischen den Schalen von außen nach innen von 3.34 Å bis 2.2 Å. Anlagen: nano1.mpg (91,8 MB); nano2.mpg (131 MB) Nutzung: Referat Informationsvermittlung der SLUB / The scope of this work is the analysis of carbon clusters of about 100 - 500 atoms. The experimental studies are at such small clusters heavy. Knowledges about thus clusters are very important, for example in the field of the nucleation of diamond on substrates, or for the carbon nano-technology (fullerene, nanotubes), or for local defects in carbon systems. There were simulated curved interfaces in diamond. Firstly with an empirical potential. Than I developed a method, in wich the defects and the structure around them are treated by a quantum mechanical algorithm and the rest with a near to ideal structure with an empirical potential. So, it is possible an accurate calculation of great systems of about 10 (high)4 atoms on wich only locally quantum mechanical methods are necessary. With this hybrid-code diamond nuclei on silicon substrate were simulated. The stability of the diamond nuclei on the silicon substrate, the critical radius of the nuclei and the changes of the nuclei during his transformation was investigated. Another field of investigations is the molecular dynamics simulation of free carbon clusters. The initial structures had spherical, ellipsoidical or square form and consists of diamond and graphite or a free form in the case of amorphous carbon. It was demonstrated that diamond transforms at higher temperatures and under irradiation in carbon onions. The genesis of the nucleus of a carbon onion with two shells was here for the first time simulated. The existence of the cross-links between the shells of a carbon onion was demonstrated. These existence was expected from the experimentators. The cross-links are the initiators of the transformation of carbon onions to diamond. The center of carbon onions is under self-pressure, because the distance between the outer shells is about 3.34 Å and between the inner shells about 2.2 Å. Appendix: nano1.mpg (91,8 MB); nano2.mpg (131 MB) Usage: Referat Informationsvermittlung/ SLUB

Ziel der Arbeit ist die theoretische Analyse von Kohlenstoff-Clustern der Größe 100 - 500 Atome. Die experimentellen Beobachtungen sind bei dieser geringen Anzahl der Atome schwierig. Anderseits sind Kenntnisse über solche Cluster sehr wichtig, z.B. für die Keimbildung von Diamant auf Substraten, oder für die Kohlenstoff-Nanotechnologie (Fullerene, Nanotubes), oder für strukturelle Defekte in Kohlenstoff-Systemen. Es wurden gekrümmte Grenzflächen im Diamant simuliert. Zuerst mit einem empirischen Potential. Es wurde danach eine Methode entwickelt, bei der die schwach gestörten Gebiete einem empirischen Potential gehorchen, und die stark gestörten Gebiete, wo eine genaue Berechnung erforderlich ist, durch eine quantenmechanische Näherung beschrieben wurden. Somit kann man mit guter Genauigkeit große Systeme, bestehend aus einigen 10 (hoch)4 Atomen, simulieren, bei denen nur lokal quantenmechanische Methoden erforderlich sind. Mit diesem Hybrid-Code wurden weiterhin Diamantkeime auf Silizium gerechnet. Es wurden Aussagen bezüglich der Stabilität des Diamants auf dem Siliziumsubstrat, der kritischen Keimgröße, der Änderungen, die der Keim erfährt, gemacht. Ein anderes Gebiet ist die molekulardynamische Simulation bezüglich der Stabilität und des Transformationsverhaltens von Kohlenstoff-Nanoteilchen. Es wurden als »Rohstoffe» sowohl Diamant- und Graphitkristalle sphärischer, ellipsoidischer oder quadratischer Form benutzt, als auch amorpher Kohlenstoff. Es wurde demonstriert, daß sich Diamant unter höherer Temperatur und Bestrahlung in Kohlenstoffzwiebeln transformiert. Es wurde der innere Kern, bestehend aus zwei Schalen, der Kohlenstoffzwiebel simuliert. Es wurde, nach meinem Wissen, zum ersten Mal gezeigt, daß zwischen den Schalen der Kohlenstoffzwiebel Quer-Verbindungen (cross-links) existieren. Diese waren von den Experimentatoren vermutet worden. Sie bilden die Initiatoren der Diamantkeime der Kohlenstoffzwiebel bei ihrer ohne äußeren Druck möglichen Transformation in Diamant. Die Zentren der Kohlenstoffzwiebeln befinden sich bereits in der Entstehung der Zwiebel unter einem Selbstdruck. Bei den größeren Kohlenstoffzwiebeln beträgt der experimentell bestimmte Abstand zwischen den Schalen von außen nach innen von 3.34 Å bis 2.2 Å. Anlagen: nano1.mpg (91,8 MB); nano2.mpg (131 MB) Nutzung: Referat Informationsvermittlung der SLUB / The scope of this work is the analysis of carbon clusters of about 100 - 500 atoms. The experimental studies are at such small clusters heavy. Knowledges about thus clusters are very important, for example in the field of the nucleation of diamond on substrates, or for the carbon nano-technology (fullerene, nanotubes), or for local defects in carbon systems. There were simulated curved interfaces in diamond. Firstly with an empirical potential. Than I developed a method, in wich the defects and the structure around them are treated by a quantum mechanical algorithm and the rest with a near to ideal structure with an empirical potential. So, it is possible an accurate calculation of great systems of about 10 (high)4 atoms on wich only locally quantum mechanical methods are necessary. With this hybrid-code diamond nuclei on silicon substrate were simulated. The stability of the diamond nuclei on the silicon substrate, the critical radius of the nuclei and the changes of the nuclei during his transformation was investigated. Another field of investigations is the molecular dynamics simulation of free carbon clusters. The initial structures had spherical, ellipsoidical or square form and consists of diamond and graphite or a free form in the case of amorphous carbon. It was demonstrated that diamond transforms at higher temperatures and under irradiation in carbon onions. The genesis of the nucleus of a carbon onion with two shells was here for the first time simulated. The existence of the cross-links between the shells of a carbon onion was demonstrated. These existence was expected from the experimentators. The cross-links are the initiators of the transformation of carbon onions to diamond. The center of carbon onions is under self-pressure, because the distance between the outer shells is about 3.34 Å and between the inner shells about 2.2 Å. Appendix: nano1.mpg (91,8 MB); nano2.mpg (131 MB) Usage: Referat Informationsvermittlung/ SLUB