Abstract: Molecular dynamics (MD) simulations are a useful computational tool in fields such as fusion research. Small but vital portions of fusion reactors are essential to their correct operation and longevity. Using the reactive bond order (REBO) and adaptive intermolecular REBO potentials, it is possible to model carbon-based systems, such as graphite diverter plates, under simulated bombardment. The degradation of these plates due to random bombardments from plasma can eventually incur costly shut downs. To gain a better understanding of the atomic-level dynamics that occur when a graphite and amorphous carbon surface undergo energetic, serial bombardment by atoms such as hydrogen, deuterium, and tritium, these two systems were evolved with the REBO and AIREBO potentials. It was found that the AIREBO potential gave different results with regards to surface evolution, sputter yield, and steady state formation. Graphite surfaces evolved to a much different steady state when compared to amorphous carbon, which lead to varied surface structure and may also lead to differing sputtering yields. An additional round of simulations was performed on graphite surfaces that were deeper in the direction normal to the surface. Based on the previous results, the AIREBO potential and two different bombardment energies were used, and the additional layers added allowed for greater fluences, defined by the number of impacts per unit area, to be achieved. As an additional improvement of the previous work, thermostats were set by using zones of control rather than employing the thermostat on the entire system, achieving atomic layer control of the thermostatted regions during the simulation. After employing these changes and evolving the simulations for only slightly larger fluences than previous simulations, the formation of voids within the graphite layers, or "bubbles", was produced. Particle build-up consisting of gaseous D, D2, and other small molecules near the penetration depth caused the formation of these bubbles. It was found for 20 eV impact energies the penetration depth is well defined, because of the lower energy of insertion. The stopping power of the potential on these low energy insertions leads to a noticable build-up of D atoms near the penetration depth. For the 80 eV simulations, the penetration depth is broadened when compared with the 20 eV simulations. The impacts penetrate more layers with increased impact energy, with bubble formation occurring away from the average penetration depth. A comparison of retention ratios is also discussed, and found that the 80 eV simulations retained more D than the 20 eV simulations. To attempt to avoid the issue of bubble formation, and to expand on the capabilities of the MD code, graphite surfaces were expanded in the directions perpendicular to the insertion direction, and the ability to bombard the surface with multiple atom types was implemented. Another improvement was introduced in the code to allow the variable time step algorithm to be used in conjunction with the thermostat. These systems yielded a closer model to experimental conditions, where the energy of interaction between the layers of graphite is larger than the insertion energy of the incident particles. While only smaller fluences compared to previous work have been achieved for these systems, the systems have shown promise in terms of their surface evolution and behavior.

This book is a stop-gap contribution to the science and technology of carbon plasmas and carbon vapors. It strives to cover two strongly related fields: the molecular quantum theory of carbon plasmas and carbon nanostructures; and the molecular and atomic spectroscopy of such plasmas and vapors. These two fields of research are strongly intertwined and thus reinforce one another.Even though the use of carbon nanostructures is increasing by the day and their practical uses are emerging, there is no modern review on carbon plasmas, especially from molecular theoretical and spectroscopic viewpoints. The importance of the present book is therefore great from both educational and practical aspects. This review might be the first step towards bringing such textbooks into existence for university education. Similarly, for applied and engineering works in carbon nanostructures, the book provides a theoretical salient point for technologists in the field.

Amorphous carbon films approximately 20 nm thick are used throughout the computer industry as protective coatings on magnetic storage disks. As storage densities increase, the role of the overcoat becomes increasingly important because of smaller spacings between the recording head and the spinning disk. Furthermore, future-generation disks call for an overcoat thickness of 5 nm or less. These small length scales and the high speed of the spinning disk (10-30 m/s) suggest that a molecular dynamics (MD) model might provide useful insight into friction and wear mechanisms when the head and disk make contact. One of the necessary inputs required to carry out such an MD model is a specification of the position of all the atoms in the simulation, i.e. a detailed model of the material microstructure. Such a detailed understanding of the microstructure of amorphous carbon overcoats does not presently exist. Neutron and electron diffraction studies demonstrate that the material is amorphous. Previous classical MD simulations yield pair distribution functions in qualitative agreement with the diffraction studies, but they all differ in detail. More recent, quantum-mechanical tight-binding MD (TBMD) studies give a better description of the interatomic interactions and the chemical hybridization (sp2-graphite-like versus sp3-diamond-like). However, these studies are presently limited to rather small system sizes and rapid quench rates. In this paper we present molecular dynamics simulations of the growth of amorphous carbon films deposited onto a diamond substrate using a bond-order potential model. This classical potential mimics the quantum mechanics allowing carbon to form strong chemical bonds with a variety of hybridizations. It was found that the system formed unphysical bonding configurations without an added torsional energy between sp2 hybridized carbon atoms. This torsional energy was included for all results presented here. 18 refs., 3 figs.

This volume collects research findings presented at the 8th Edition of the Electronic Structure: Principles and Applications (ESPA-2012) International Conference, held in Barcelona, Spain on June 26-29, 2012. The contributions cover research work on methods and fundamentals of theoretical chemistry, chemical reactivity, bimolecular modeling, and materials science. Originally published in the journal Theoretical Chemistry Accounts, these outstanding papers are now available in a hardcover print format, as well as a special electronic edition. This volume provides valuable content for all researchers in theoretical chemistry, and will especially benefit those research groups and libraries with limited access to the journal.

It became clear in the early days of fusion research that the effects of the containment vessel (erosion of "impurities") degrade the overall fusion plasma performance. Progress in controlled nuclear fusion research over the last decade has led to magnetically confined plasmas that, in turn, are sufficiently powerful to damage the vessel structures over its lifetime. This book reviews current understanding and concepts to deal with this remaining critical design issue for fusion reactors. It reviews both progress and open questions, largely in terms of available and sought-after plasma-surface interaction data and atomic/molecular data related to these "plasma edge" issues.

World experts in amorphous carbon have been drawn together to produce this comprehensive commentary on the current state and future prospects of amorphous carbon, a highly functional material. Amorphous carbon has a wide range of properties that are primarily controlled by the different bond hybridisations possible in such materials. This allows for the growth of an extensive range of thin films that can be tailored for specific applications. Films can range from those with high transparency and which are hard and diamond-like, through to those which are opaque, soft and graphitic-like. Application areas including field emission cathodes, MEMs, electronic devices, medical and optical coatings are now close to market.

Molecular dynamics computer simulations are used to study the effect of substrate temperature on microstructure of deposited amorphous hydrogenated carbon (a:CH) films. A transition from dense diamond- like films to porous graphite-like films is observed between substrate temperatures of 400 and 600 K for a deposition energy of 20 eV. The dense a:CH film grown at 300 K and 20 eV has a hardness ((approximately)50 GPa) about half that of a pure carbon (a:C) film grown under the same conditions.