The main goal is to develop, test and apply novel abinitio simulation methods that allow to generate and analyze (in terms of real time based properties) approximate quantum dynamics for complex molecular many-body systems in the rage to 10-100 atoms. Finite systems such as floppy molecules, quantum clusters and condensed matter systems such as water will be covered. The tools chosen are the Car Parrinello method combined with abinitio path integrals. Quantum corrections to the classically autocorrelation function of the dipole operator will be analyzed theoretically first and the assessed numerically based on exact solutions for simple models. In a third step an abinitio path integral molecular dynamics technique will be used to simulate time dependent properties of quantum systems. The system applications will cover floppy molecules as CH5+, C2H3+, HSO2+, H302-. Very interesting is the case of CH5+, where it remains to be seen if the IR spectrum of the C-H stretching band can be computed. Important is the case of quantum corrections to the scattering function, that although some of the approximations are widely used, yet remains unclear the validity and exactness of the approximations. Once the tools and techniques necessary to calculate them are ready, the approximations will be theoretically and numerically applied to real systems such as liquids at low temperatures. The special case of D20 and H2O will be studied.