Date of Graduation

Summer 2021

Degree

Master of Science in Materials Science

Department

Physics, Astronomy, and Materials Science

Committee Chair

Ridwan Sakidja

Keywords

interatomic potential, molecular dynamics, thermal properties, zirconium diboride, ultra-high temperature ceramics

Subject Categories

Ceramic Materials

Abstract

Embedded Atom Method (EAM) and Modified-EAM (MEAM) interatomic potentials were developed for zirconium diboride (ZrB2). The EAM and “Reference Free” (RF) version of the Modified Embedded Atom Method (RFMEAM) potentials have been fitted by utilizing Density Functional Theory (DFT)-based datasets including lattice deformations and high-temperature ab-initio molecular dynamics (AIMD) simulation results. The occupancies of phonons for acoustic phonon modes from the density functional theory calculation shows that these modes of vibration, mostly due to heavier mass element (Zr), which occur below 8.711 THz, while a slight underestimation to that of DFT calculation predicted by EAM below 8.439 THz and an overestimation predicted by RF-MEAM below 8.880 THz. Consequently, the frequency shifting of acoustic phonon modes for heavier mass element (Zr) on EAM and RF-MEAM potential models results in a similar frequency shifts on optical modes which is mostly due to lighter element (B); the frequency range for optical modes is 12.013-22.733 THz for EAM and 12.616-23.957 THz for RF-MEAM models compared to the frequency range of 12.181-23.124 THz by DFT calculation. In addition, the bulk modulus of ZrB2 for EAM and RF-MEAM potential models are 263.81 GPa and 254.78 GPa compared to that of ground state DFT calculation of 238 GPa. Overall, the results showed that the applicability of EAM and RF-MEAM to modeling the interatomic potentials of the diboride system.

Copyright

© Bikash Timalsina

Open Access

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