Atomistic Field Theory of Nano Energy Harvesting

This paper aims to formulate nanoscale energy harvesting and nanoscale piezoelectrics using Atomistic Field Theory. The theoretical construction, including polarization, induced electric potential, induced electric field and balance law of electric field (Maxwell's Equation), is introduced and the computational scheme, Generalized Atomistic Finite Element Method (GAFEM), is briefly addressed. This field theory connects mechanical displacement directly to electric polarization from atomistic perspective. The corresponding induced potential field and induced electric field can be calculated from polarization of all unit cells. It is a nonlinear, nonlocal and dynamic theory and can be serve as a fundamental formulation in nanoscale electromechanical coupling and nanoscale energy harvesting. A computational example of nano-piezoeletricity is studied. A perovskite type nano-cube made of barium titanate is subjected to a simple tensile loading. The resultant induced electric potential is shown. It demonstrates how the induced electric potential connects with the mechanical displacement, which is related to nano-piezoeletricity. This study also finds a threshold for induced electric potential exists at nanoscale. If the applied loading is too large to sustain the electric potential, the potential field will be released and piezoelectric effect disappears. This theory and computational scheme can be utilized to study Nanogenerator and analyze nanoscale piezoelectronic mechanics and nanoscale energy harvesting.