Anisotropy of crystal structure distortion in organic molecular crystals of drugs induced by hydrostatic compression

Variation of the unit cell parameters of paracetamol and phenacetin as a fu nction of hydrostatic pressure was studied by X-ray diffractometry in diamo nd anvils. At elevated pressure (4 GPa). the crystal structures undergo ani sotropic distortion. The greatest compression was observed in the direction s in which the molecules are linked by van der Waals forces alone. Compress ibility of the structures in the direction of hydrogen depends on the prese nce of other types of interaction and on molecular arrangements in the crys tals. In the case of paracetamol, integrated compression of the structure l ed to its stretching in definite crystallographic directions.