X-ray absorption fine structure (XAFS) was first invented from 70’s of the 20th century. It has been one of the most powerful techniques for structural investigation. In this method, structure is revealed based on photoelectron wave interference between the outgoing wave, that is emitted from an atom when it absorbs x-ray, and the scattered wave that is bounced off by neighboring atoms. XAFS is an element-specific probe of a structure about a specific atom of interest. The limitation of XAFS is that the photoelectron mean free path is relatively short and thereby only the short-range structure about the ion is probed. The more structural order the larger structure range can be probed. It can easily reach a structural accuracy of 0.01 Å... more