Diverse Local Structures in Simulated Amorphous SiO2

Open Access
Author:
Dormier, Adam Matthew
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Scott T. Milner, Thesis Supervisor
  • Darrell Velegol, Honors Advisor
Keywords:
  • silica
  • glasses
  • simulation
  • computational
  • molecular dynamics
  • local structure
  • SiO2
Abstract:
Amorphous silica lacks the global periodic structure present in its crystalline counterparts (quartz, tridymite, crystoballite, etc.), and this leaves open the question of what its structure actually looks like, as well as how it can be effectively described. We apply a method rooted in graph theory to identify and label local structural arrangements within glasses generated by molecular dynamics (MD) simulations. The focus on atomic connectivities makes this methodology structure-agnostic, and enables the search for recurring structural motifs within the system. We observe the distribution of local structures over a range of temperatures which straddle the glass transition in an effort to determine whether a relationship exists between the dynamics of the system as it undergoes glass transition and its internal structure. To this end, we also consider the lifetimes of the observed local structures as the temperature of the system is varied. Additionally, we simulate glasses under various annealing conditions in order to observe the impact of the preparation of a glass on its structure.