Elastic scattering of electrons from a frozen lattice configuration is treated as time-independent. The first theoretical objective in treating dynamic inelastic electron scattering is to average statistically over the quasielastic electron diffraction patterns produced by various crystal configurations before numerical calculations. Green’s function theory is probably the method best suited for this purpose. For simplicity, we start with the equation of single inelastic electron excitation with consideration for the time-dependent (or configuration-dependent) thermal vibration perturbation on the crystal potential \((\Delta V)\) .