Electron‒Phonon Coupling from First Principles

The development of a model that treats the electron‒phonon system of a crystal as a system of new quasiparticles, where both the electron and phonon properties of the system are taken into account, is reported. The Hamiltonian describing these quasiparticles is derived from first principles and, on its basis, elements of the dynamic matrix are obtained for the case of a monoatomic crystal. It is shown that, unlike the classical theory, the dependence of the dynamic matrix on the lattice vectors is integral.