ICME overview of shape memory effect on Bismuth Ferrite ceramic
Shape memory materials have drawn tremendous attention and interest in recent years for a wide range of applications including coupling, sensing, and actuating, as a result of their special and extraordinary abilities to recover certain configurations under proper thermomechanical conditions. To understand, design and improve the shape memory effect of bismuth ferrite, the multiscale model of integrated computational materials engineering (ICME) method is applied.
Multi-length scale approach is used to understand, improve and predict the Bismuth ferrite shape memory effect through each individual length scales. The macroscopic phenomenological model is used to define the lower length scale effects on the macroscale stress-strain materials behavior. To understanding the phase transformation at the macroscale, the model of mesoscale is required for deformation mechanisms. In order to capture the deformation mechanisms at mesoscale, the microscale behavior of dislocation and nucleation is important to investigate. To model the dislocation motion, the parameters such as stacking fault energy and vacancy formation energy for dislocation mobility are from the atomistic scale. To define the behavior of the atomistic scale, the ground state properties with lattice structure from the electronic scale are required.
The lowest length scale to start is the electronic scale. Density Function Theory (DFT) calculations are applied on the electronic scale to determine the ground state properties of materials such as elastic constant, bulk modulus, and lattice structure. In this scale, the open source software Quantum Espresso is used for the analysis. Software such as Xcrysden is used to visualize the crystal structure, which is then validated with the Library of Crystallographic Prototypes and the American Mineralogist Crystal Structure Database.
At the atomistic scale, properties such as vacancy formation energy and stacking fault energy are calculated. Quantum Espresso is also used to approach these calculations. It is worth mentioning that the Modified Embedded Atom Method (MEAM) is used to obtain all the parameters for the materials. Software such as LAMMPS and MATLAB are also used for this step. At the microscale, the dislocation mobility is calculated for dislocation motion. Also, the dislocation interaction energy and nucleation are calculated to predict the microscale behaviors by using the microscopic models and micromechanics based macroscopic models. At mesoscale, the grain size and boundary are two main factors that affect the deformation, response, and stability in macroscale. At macroscale, the macroscopic phenomenological model is used to obtain the stress-strain relationship.