The effect of the angle of «meeting» of fullerite C60 with a solid substrate on the deposition process

Carbon forms a large number of allotropic forms, one of which is fullerene. Fullerene is a convex closed polyhedron with carbon atoms at its vertices. The most common is fullerene, consisting of 60 carbon atoms and designated - C60. In turn, fullerenes are able to agglomerate, forming a molecular crystal - fullerite. In the interaction of fullerite C60 with a solid, it is possible to deposit on the surface of the body both whole fullerite and the fullerenes that form it. The interaction process in the C60 fullerite system - the substrate of a solid, and then on - the fullerite - substrate system - is multi-parameter. So, when modeling the interaction of fullerite with a substrate, the following were taken into account: the temperature of the system - 300, 700, 1150 K; the speed of fullerite movement is 0.005, 0.01, 0.02 Å / fs. In addition, in the study, we varied the angle between the fullerite velocity vector and the normal to the contact surface of the substrate, called the “meeting angle”. An iron crystal Fe (100) was modeled as a solid body substrate, as one of the most common structural materials. Fullerite C60 was in contact with the solid substrate with its face. Computer simulation of the process of contact of fullerite C60 with the substrate was carried out in the LAMMPS software package. The main result of this study is to determine the effect of the angle of “meeting” of C60 fullerite in contact with a solid substrate, which will significantly complement the overall picture of the process of C60 fullerite deposition. In turn, this can allow the creation of various films and wear-resistant coatings on the surface of materials.

Pop-in behavior and elastic-to-plastic transition of polycrystalline pure iron during sharp nanoindentation

This study analyzes the elastic-to-plastic transition during nanoindentation of polycrystalline iron. We conduct nanoindentation (Berkovich indenter) experiments and electron backscatter diffraction analysis to investigate the initiation of plasticity by the appearance of the pop-in phenomenon in the loading curves. Numerous load–displacement curves are statistically analyzed to identify the occurrence of pop-ins. A first pop-in can result from plasticity initiation caused by homogeneous dislocation nucleation and requires shear stresses in the range of the theoretical strength of a defect-free iron crystal. The results also show that plasticity initiation in volumes with preexisting dislocations is significantly affected by small amounts of interstitially dissolved atoms (such as carbon) that are segregated into the stress fields of dislocations, impeding their mobility. Another strong influence on the pop-in behavior is grain boundaries, which can lead to large pop-ins at relatively high indentation loads. The pop-in behavior appears to be a statistical process affected by interstitial atoms, dislocation density, grain boundaries, and surface roughness. No effect of the crystallographic orientation on the pop-in behavior can be observed.

Theory and Computer Simulation of Quantum NEMS Energy Storage in Materials

The theory of quantum relaxation of the nanoelectromechanical system (NEMS) energy storage in materials is taken under consideration. By using the method of quantum NEMS kinetics (NK) the relaxation NEMS energy storage in the form of limited planes (100) Fe 172 cube in fcc iron crystal was studied. For comparison, the calculation a similar structure atomic cluster Fe 172 was carried out by the molecular dynamics method (MD) for temperature T = 293 K. Analysis of computer-related experiments have shown that the relaxation of the NEMS energy storage Fe 172 and the MD atomic cluster Fe 172 from an initial nonequilibrium state has significant differences both in the kinetics, and in a variety of structural transformations. It is shown that the iron MD cluster relaxation is insignificant and its final total binding energy per atom is 2 eV/at lower than the crystal one. The NK-method revealed that after relaxation there is a significant change in the shape and the pair radial distribution function of nuclei the NEMS energy storage. It significantly increases the binding energy up to 3.34 eV/at, which is only about 1 eV/at less than the binding energy of the crystalline iron. It is shown an opportunity to undergo a process of self-organization the NEMS energy storage through several intermediate metastable states. It is manifested that fluctuation rebuild the cube into a cuboid with a strong bending of the cube surfaces occurs at 20 ps of relaxation, and there is the second transformation being with trapezoid change of faces at 40 ps of relaxation process. This effect cardinally differentiates NK relaxation of the NEMS energy storage cube Fe 172 from MD relaxation of the atomic cluster Fe 172 in the crystalline iron.

MECHANICAL PROPERTIES AND TOPOLOGICAL CHANGES IN A Fe-CRYSTAL WITH FIXED AND MIGRATING H-ATOM: A NUMERICAL STUDY

A numerical study, within the framework of molecular statics, is conducted to assess the effect of a fixed and migrating hydrogen atom on the stress–strain data and the topological changes taking place in a 3D BCC α-iron crystal subjected to a tensile elongation. A pair-wise Morse potential is used to describe the interatomic forces. The results for a crystal with 2324 iron atoms show that the presence of a hydrogen atom, either migrating or fixed, produces relatively small effect on the stress–strain data within the elastic and some plastic range of loading. However, the topological changes, represented by the changes in the nearest neighbors for each atom within the cut-off distance after each displacement increment, are substantially different. Similarly, a comparison of the changes in the atomic potential energies when the sudden drop in stresses takes place shows differences between the two cases.