Structure Redetermination and Packing Analysis of Aspirin Crystal

The crystal structure of aspirin has been redetermined by X-ray diffraction analysis at room temperature. The lattice energy, the eleastic constants and the structure parameters corresponding to the equilibrium of a model potential of aspirin crystal have been calculated by taking account of the non-rigidity of the molecule and applying the condition of vanishing stress. The model potential consists of the exp-6 type dispersion and exchange repulsion terms, the Lippincott type hydrogen bond stretching terms and the electrostatic interaction terms between fixed atomic charges. The atomic coordinates of the calculated structure agree well with those determined crystallographically.