Phononic Crystals - Plane Wave Expansion Method
Adapted from the plane wave expansion method used for photonic crystals. This technique expands parameters such as elastic constants and density into Fourier series, combines with Bloch's theorem, and expresses the elastic wave equation in reciprocal lattice space as a superposition of plane waves. The program provides a detailed implementation with comprehensive annotations for easy understanding, including key algorithmic steps and function descriptions for Fourier coefficient calculations and eigenvalue problem solving.