From Atoms to Continuum: A Multi-scale Multi-Phenomena Theory

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From Atoms to Continuum: A Multi-Scale Multi-Phenomena TheoryJames D. Lee and Youping ChenSchool of Engineering and Applied ScienceThe George Washington UniversityAbstractIn ABO3 ferroelectrics, the displacements of ions at sub-nanometer scale account for the piezoelectricity and the polarization reorientation. Grain and grain boundary structures, from nano- to micro-scale, of a macroscopic ceramics remarkably influence the electromechanical response. The physics of ferroelectrics is multi-scale in nature. The objective of this research is to enhance the scientific understanding of multi-scale multi-physics phenomena. We will start from atomistic lattice dynamics, through statistical mechanics, molecular dynamics simulations and microcontinuum modeling, to link atomic model to micromorphic electromechanical theory, and to investigate the fully coupled thermo-electro-mechanical response of ferroelectric ceramics. This research is expected to be an important step forward for microcontinuum theories by finding the material parameters from atomistic models. It will be applicable to problems in a wide range of length and time scales from nano- to macroscopic. If successful, it will have immediate engineering applications, including sensors, actuators, capacitors and memory devices, etc.