Date of Award
M.S. in Engineering Science
University of Mississippi
The structural and mechanical properties of void-free and single-void α-quartz were investigated using MD simulations with three different interatomic potentials (BKS, Vashishta and Tersoff). Two distinct ensembles, NVT and NPT, were separately applied to investigate the tensile response of α-quartz under uniaxial strain and uniaxial stress states. A comprehensive comparison among different potentials, as well as comparison with currently available experiments, has been made. The BKS and Vashishta potentials accurately predicted the structural properties of void-free α-quartz, while the Tersoff potential was deviated significantly from the experimental data. Under tension, the BKS did a better description for the mechanical performance of α-quartz. The Vashishta potential also captured the tension behavior, but overpredicted the Young’s modulus. The Tersoff potential accurately described the elastic deformation but was unable to predict the fracture behavior for α-quartz. Furthermore, the void-size effect on the tensile and fracture behavior of α-quartz was analyzed and the predictions by using all three potentials were compared. Additionally, the choice of the ensembles could influence the mechanical response of α-quartz. The presence of a small void with a radius of 2.5 Å, when using an NVT ensemble with the BKS potential, significantly affected the tensile properties, while the NPT simulation did not show the same effect. The tensile curves obtained by using the Vashishta potential were similar in both NVT and NPT simulations, with slightly higher tensile properties observed in the NPT simulation. With Tersoff potential, brittle fracture occurred at a strain of 0.33 in NVT simulation but was not observed in NPT simulation. The equivalent stress analysis reveals that the BKS potential can better describe the stress concentration around the voids, while the Vashishta and Tersoff potentials cannot show satisfactory description on the material fracture with the presence of the voids. Based on all the above-mentioned comparisons, the BKS potential is demonstrated to be the most suitable one to describe α-quartz under tension. All the findings in this work highlight the importance of a proper selection of interatomic potentials for simulating the properties of nanovoid structures, especially for the study of fracture mechanisms in silica materials.
Jia, Yu, "Molecular Dynamics Simulations for The Mechanical Behavior of Alpha Quartz with Void Defects Under Tension" (2023). Electronic Theses and Dissertations. 2686.
Available for download on Sunday, October 06, 2024