The School of Mechanical and Materials Engineering Seminar Series, “Mechanical Properties and Deformation Behavior of Doped Rare-Earth Oxides: An Atomistic Approach” Presented by Azmain Faek Islam

About the event

Mechanical Properties and Deformation Behavior of Doped Rare-Earth Oxides: An Atomistic Approach

Presented by Azmain Faek Islam, Ph.D. Candidate, School of Mechanical and Materials Engineering, Washington State University

Abstract

Rare-earth–doped cerium oxide (CeO₂) exhibits strong infrared absorption and a rich defect chemistry that makes it indispensable across optical, catalytic, ionic, and high-temperature applications. While the influence of dopants and oxygen vacancies on its structural behavior is broadly understood, this work advances that understanding by probing how specific dopant chemistries, vacancy topologies, and lattice distortions collectively govern mechanical response and strain-induced phase evolution at the atomic scale. In this work, large-scale classical molecular dynamics simulations, supported by spin-polarized density functional theory, are employed to elucidate how aliovalent dopants, EuO_1.5, GdO_1.5, YO_1.5, and isovalent ZrO₂ modify the fluorite lattice across both small and large deformation regimes. Elastic property calculations reveal systematic mechanical softening in trivalent-doped systems, where charge-compensating oxygen vacancies introduce local lattice distortions, weaken cation–anion cohesion, elevate potential energy around defect sites, and reduce all major elastic moduli relative to pure CeO₂. Thermodynamic analyses demonstrate that vacancy topology and dopant–vacancy clustering drive mechanical degradation by creating heterogeneous energy landscapes and stress-sensitive weak regions, whereas tetravalent Zr⁴⁺ substitution preserves stoichiometry and enhances lattice integrity through stronger metal–oxygen bonding. Under uniaxial tensile loading, dopant chemistry and concentration are shown to dictate the onset of disorder, dislocation activity, and non-fluorite structural transitions: trivalent dopants accelerate strain localization, vacancy-mediated instabilities, and early amorphization, reducing strain-to-failure by up to 75% at high concentrations, while ZrO₂ doping promotes more gradual transformation kinetics and greater deformation tolerance. Polyhedral Template Matching and radial distribution analyses further reveal asymmetric responses of the cation and oxygen sublattices, indicating a decoupling of structural stability pathways under strain that becomes increasingly pronounced with vacancy density. Together, these findings establish a unified atomistic framework linking elastic softening, cohesive energetics, and strain-induced phase evolution in rare-earth-doped CeO₂, providing quantitative guidance for designing fluorite-structured ceramics with tunable stiffness, enhanced toughness, and improved resistance to mechanically driven degradation in demanding structural, energy, and thermal environments.

Biography

Azmain Faek Islam is a doctoral candidate in Mechanical Engineering at Washington State University. He conducts his research the Computational Nanoscience Laboratory (CNL!) under the supervision of Dr. Soumik Banerjee. His work integrates molecular dynamics, ab-initio simulations, and multiscale modeling to explore the behavior of ionic crystalline and amorphous materials in extreme and extraterrestrial environments. His research spans ionic-liquid based metal extraction for NASA In-Situ Resource Utilization (ISRU) missions, defect chemistry and mechanical behavior of rare-earth–doped ceria, and molten salt systems containing actinides and lanthanides. He has also worked in collaboration with CNL! and the U.S. Army Research Laboratory (ARL) on dopant-induced phase stability in CeO₂ and contributed to predictive modeling of irradiation response and strain-driven phase evolution in oxide ceramics. Beyond fluorite oxides, he has performed benchmark simulations on silicon carbide (SiC), evaluating the performance of machine-learned and classical interatomic potentials and analyzing generalized stacking-fault energy landscapes to understand defect-mediated deformation mechanisms. His earlier work includes classical and ab initio MD along with modeling hybrid perovskite tandem solar cells using SCAPS, with publications in IEEE Transactions on Electron Devices, The Journal of Physical Chemistry B, and RSC Advances. Azmain has taught core undergraduate materials engineering courses and collaborated closely with experimental groups to validate and interpret multiscale simulation predictions. His research advances the fundamental understanding of ionic interactions, defect-mediated mechanics, and the design of materials capable of withstanding extreme environments.