@misc{RichterSmith1996, author = {Richter, Asta and Smith, Roger}, title = {Surface Growth Modes analysed with Modern Microscopic and Computing Techniques}, series = {Wissenschaftliche Beitr{\"a}ge 1/1996}, volume = {2}, journal = {Wissenschaftliche Beitr{\"a}ge 1/1996}, number = {1}, issn = {0949-8214}, doi = {10.15771/0949-8214_1996_15}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-8258}, pages = {72 -- 78}, year = {1996}, abstract = {It is demonstrated how new microscopes with atomic resolution in combination with modern fast computers and computational techniques can be used in a complementary way in the analysis and explanation of crystal growth on surfaces. Examples are given of spiral formation, fractal growth, fullerene formation and the growth of C60 films.}, language = {en} } @misc{SmithRichterRies1998, author = {Smith, Roger and Richter, Asta and Ries, Ronald}, title = {Foundations of a Virtual Laboratory}, series = {Wissenschaftliche Beitr{\"a}ge 2/1998}, volume = {4}, journal = {Wissenschaftliche Beitr{\"a}ge 2/1998}, number = {2}, issn = {0949-8214}, doi = {10.15771/0949-8214_1998_2_24}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-7689}, pages = {120 -- 124}, year = {1998}, abstract = {A project was funded by the European Union to build foundations for a virtual laboratory where experimental and theoretical results could be combined into an audio-visual interactive presentation through the use of modern computers. The process of thin film growth and modification by energetic ion beams was chosen as the first topic for this new educational tool. Different models for thin film growth are developed and compared to experimental results in the presentation. Particular examples include spiral formation, modelled using cellular automata, island growth using Monte-Carlo methods and the first few layers of growth using classical molecular dynamics. Most of the examples are related to the growth of C60 films for which a number of experimental results had been obtained and previously reported in this journal [1]. The principle property under investigation was the structure and morphology of the films. Nine separate computer movies of the dynamics of these processes were developed on a fast PC under Windows95 and incorporated into a computer presentation made using the Authorware package. Experimental images obtained from a scanning force microscope were also included and compared to the computer models along with music and verbal explanation. In addition to the interactive version of the multi-media presentation, a non-interactive version was also made which is suitable for lectures or conference presentation. This version lasts approximately 25 minutes. Approximately 100 CD's of this work were made and are being distributed to various laboratories. A copy of the CD is available on request.}, language = {en} } @article{SmithChristopherKennyetal.2003, author = {Smith, Roger and Christopher, D. and Kenny, Steven D. and Richter, Asta and Wolf, Bodo}, title = {Defect generation and pileup of atoms during nanoindentation of Fe single crystals}, series = {Physical Review B}, volume = {67}, journal = {Physical Review B}, number = {24}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14855}, year = {2003}, abstract = {Complementary large scale molecular-dynamics simulations and experiments have been carried out to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe {110}, {100}, and {111}. The defect formation and motion causes the complex mechanisms of plastic and elastic deformation which is reflected in the pileup patterns. The experimental results show distinct patterns of pileup material which are dependent on the individual crystal faces and the superposition of the stress field of the indenter. The highest pileup around the indenter hole occurs on the {100} surface and the shallowest on {111}. The least symmetric surface is {110} which produces an experimental pileup pattern displaying only twofold symmetry with the axially symmetric indenter. The pyramidal indenter produces an asymmetric pattern which changes as the crystal is rotated with respect to the tip but repeats with threefold rotational symmetry. Material displacement occurs primarily in planes of the {110} family. Pileup is formed by cross slip between planes of the same family which intersect in ⟨111⟩ directions. For the {110} surface, dislocation loops propagate in the four in-plane ⟨111⟩ directions and the two inclined ⟨111⟩ directions. The loops that propagate in the in-plane directions are terminated by edge dislocations at the surface. These transport material away from the tip but cannot produce pileup. The loops that propagate in the inclined direction cross slip and cause the observed pileup. The {100} surface has fourfold rotational symmetry and all the ⟨111⟩ directions are inclined. The dislocation loops propagate in these directions and cross slip readily occurs, leading to a large pileup. The {111} face shows the least pileup which is more spread out over the surface. In this case the dislocation loops propagate in shallow slip planes and do not readily cross slip. Experimentally determined force-depth curves show distinct "pop-ins" which correspond to the formation of dislocations. The contact pressure (nanohardness) is not a constant and increases with decreasing indentation depth. It also changes with crystal face. Calculated force-depth curves match the experimental trend but give estimates of the nanohardness and Young's modulus higher than those values experimentally determined.}, language = {en} }