In this communication the lattice dynamics and allied properties of RbBr crystal we have investigated theoretically by use of Van der Waal three body force shell model. Elemental rubidium has a NaCl-type crystal structure which is highly reactive, with properties similar to those of other alkali metals. The investigation of of the crystals depends on the motion of the constituent atoms, which can be achieved from the theoretical models of inter ionic potentials. The new proposed model, van der Waals three body force shell (VTBFS) come in existence ,which incorporates the effects of the van der Waals interaction with long-range Coulomb interactions, three-body interactions and shortrange second neighbour interactions in the framework of rigid shell model (RSM). The obtained theoretical results for Debye temperature variation, two phonons IR/Raman spectra, third order elastic constants (TOEC), fourth order elastic constants (FOEC) and the pressure derivatives of second order elastic constants (SOEC) for RbBr are very close agreement with experimental result.
