Relativistic Green's-function method for solids and molecules

The relativistic multiple-scattering method (Green's-function method) for crystals and molecules is developed from the definition of the four-component wave function in the two regions. The secular equation is obtained by matching the wave functions at the two sides of the sphere surface separating the two regions. The secular equation is expanded in powers of $\frac{1}{c^2}$ so as to exhibit the mass and spin-orbit corrections. As an application of the method we present the results for the band structure of lead.