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

从原子到连续统：多尺度多现象理论李有平工程与应用科学学院乔治华盛顿大学摘要在ABO3铁电材料中，离子在亚纳米尺度的位移引起了压电性和极化重定向。宏观陶瓷的颗粒和晶界结构，从纳米到微米，对机电响应有显著的影响。铁电材料的物理本质上是多尺度的。这项研究的目的是增进对多尺度多物理现象的科学理解。我们将从原子论晶格动力学出发，通过统计力学、分子动力学模拟和微观连续谱模拟，将原子模型与微观机电理论联系起来，研究铁电陶瓷的热-电-机械全耦合响应。通过从原子模型中寻找材料参数，这项研究有望成为微观连续谱理论向前迈出的重要一步。它将适用于从纳米到宏观的各种长度和时间尺度的问题。如果成功，它将立即在工程上应用，包括传感器、执行器、电容器和存储设备等。

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.