Microscopic theory for nanotube piezoelectricity

We combine ab initio, tight-binding methods and analytical theory to study piezoelectric effect of boron nitride nanotubes. We find that piezoelectricity of a heteropolar nanotube depends on its chirality and diameter and can be understood starting from the piezoelectric response of an isolated planar sheet, along with a structure specific mapping from the sheet onto the tube surface. We demonstrate that a linear coupling between the uniaxial and shear deformation occurs for chiral nanotubes. Our study shows that piezoelectricity of nanotubes is fundamentally different from its counterpart in three-dimensional bulk materials.