Pressure- and temperature-induced phase transitions in 2,4,6-trichloro-1,3,5-triazine crystal

The effects of pressure and temperature on the frequencies and band structu res of the Raman active inter- and intramolecular vibrations of 2,4,6-trich loro-1,3,5-triazine crystal were studied. The changes in the Raman frequenc y, band width, and band structure of both the inter- and intramolecular vib rations induced by changes of pressure and temperature indicate that (1) a displacive phase transition caused by a shear distortion of pi -stacked lay er structure may take place under about 1.7 GPa at 298 K and (2) the interm olecular nitrogen-chlorine donor-acceptor attractive interactions supportin g the extensive network structure in crystal have a direct effect upon the totally symmetric C-Cl stretching vibration.