To predict the beam dynamics in particle accelerators, the electromagnetic fields caused by the motion of charged particles need to be simulated. To account for the full set of particle motion and Maxwell's equations, full electromagnetic particle-in-cell (EM-PIC) codes offer the most accurate simulation approach. However, they are computationally too expensive for most practical applications. Hence, common simulation approaches neglect surrounding surfaces (space charge solver) or changes in the bunch structure (wake field solvers), respectively, while offering modeling advantages for different aspects of the beam dynamics. Coarsely speaking, simulations of space charge effects are of high interest in low-energy or highly dynamic parts of the accelerator, while wake field simulations are applied in high-energy parts to determine the influence of variations in the surrounding chamber geometry. We have developed a novel approach that combines the advantages of both methods using a scattered field formulation. Herein, the total field is decomposed into an incident and a scattered field component. The incident field is computed by a space charge solver, assuming particle motion in free space. Then, enforcing appropriate boundary conditions at the chamber walls, the scattered field component corresponding to geometric wake fields can be computed. With this decomposition we can use simulation approaches that are tailor-made for the space charge and wake field part, respectively. The coupling enables us to simulate the beam dynamics including transient electromagnetic waves in a self-consistent manner while keeping the computational cost at a reasonable level. We can thus predict the beam dynamics taking into account the influence of the surrounding chamber geometry in a rigorous manner, yielding new insights into, for example, the effects in injectors or bunch compressors.