Dirac's equation provides the most rigorous basis known for many calculations in relativistic quantum mechanics. A set of dynamical equations having greater intuitive content can be derived from Dirac's equation without any approximations. These secondary equations govern the properties of a Dirac particle as functions of time and space and are similar to the corresponding equations governing a classical charged fluid. Several new density functions are implied by these equations and are appropriate for incorporation into the various semiclassical models of physics.
Abstract: \n The possibility of transformation of the Dirac equation for central field standard form to the one, analogic to Scroedinger equation for each of radial parts components of wave function is considered. On this basis the conclusion about possibility of applicability of semiclassical approximation to the Dirac equation is obtained, its WKB solutions are calculated. The methods of solutions approximation in the neighborhood of turn points is analyzed, the validity of phase method [3] adaptability to receipt of semiclassical energy levels from Bohr-Sommerfeld condition is demonstrated.