The well known quasi-exact solvability of Schrödinger equation with Coulomb-like potentials is shown to survive a minimally relativistic improvement of the kinetic energy operator .
The relativistically corrected Schr\"odinger (RS) equation [(m2c4+p2c2)1/2 +V-E]\ensuremath{\Psi}=0 is sometimes used to describe charged fermions, which are subject to strong Zitterbewegung. Since, however, equations of this type describe bosons with weak Zitterbewegung effects, it is mandatory to screen the Coulomb potential V in an r range of order h/mc, and also to add a screened spin-orbit potential. Thereby the singularity problems with Coulomb potentials are avoided. While the Pauli Hamiltonian must not be used in variational or eigenvalue equations, the RS Hamiltonian may be. An effective potential for the RS equation is derived, which yields relativistically corrected energies and wave functions for fermion systems with Coulomb potentials. Accurate numerical solutions for an unshielded single-center Coulomb potential are presented.
In this paper, we examine quantum systems with relativistic dynamics. We show that for a successful description of these systems, the application of Galilei invariant nonrelativistic Hamiltonian is necessary. To modify this Hamiltonian to relativistic dynamics, we require precise relativistic kinetic energy operators instead of nonrelativistic ones for every internal (Jacobi) coordinate. Finally, we introduce and investigate the Schrödinger equation with relativistic dynamics for two-particle systems with harmonic oscillator and Coulomb potentials.