3 research outputs found
A ReaXFF carbon potential for radiation damage studies
Although molecular dynamics simulations of energetic impacts and collision cascades in graphite have been investigated for over 25 years, recent investigations have shown a difference between the types of defects predicted by the commonly used empirical potentials compared to ab-initio calculations. As a result a new ReaXFF potential has been fitted which reproduces the formation energies of many of the defects predicted by the ab-initio calculations and the energy pathways
between different defect states, important for investigating long term defect evolution. The data sets in the fitting have been have been added to the existing data sets used for modelling hydrocarbons and fullerenes. The elastic properties of the potential are less well modelled than the point defect structures with the elastic constants c33 being too high
and c44 too low compared to experiment. Preliminary results of low energy collision cascades show many point defect structures develop that are in agreement with those predicted from the ab-initio results
Development of a ReaxFF potential for Ag/Zn/O and application to Ag deposition on ZnO
A new empirical potential has been derived to model an Ag–Zn–O system. Additional parameters have been included into the reactive force field (ReaxFF) parameter set established for ZnO to describe the interaction between Ag and ZnO for use in molecular dynamics (MD) simulations. The reactive force field parameters have been fitted to density functional theory (DFT) calculations performed on both bulk crystal and surface structures. ReaxFF accurately reproduces the equations of state determined for silver, silver zinc alloy and silver oxide crystals via DFT. It also compares well to DFT binding energies and works of separation for Ag on a ZnO surface. The potential was then used to model single point Ag deposition on polar (000View the MathML source1¯) and non-polar (10View the MathML source1¯0) orientations of a ZnO wurtzite substrate, at different energies. Simulation results then predict that maximum Ag adsorption on a ZnO surface requires deposition energies of ≤ 10 eV
Evolution of Glassy Carbon Derived from Pyrolysis of Furan Resin
Glassy carbon (GC) material derived from pyrolyzed furan
resin
was modeled by using reactive molecular dynamics (MD) simulations.
The MD polymerization simulation protocols to cure the furan resin
precursor material are validated via comparison of the predicted density
and Young’s modulus with experimental values. The MD pyrolysis
simulations protocols to pyrolyze the furan resin precursor is validated
by comparison of calculated density, Young’s modulus, carbon
content, sp2 carbon content, the in-plane crystallite size,
out-of-plane crystallite stacking height, and interplanar crystallite
spacing with experimental results from the literature for furan resin
derived GC. The modeling methodology established in this work can
provide a powerful tool for the modeling-driven design of next-generation
carbon–carbon composite precursor chemistries for thermal protection
systems and other high-temperature applications