Phase diagram and crystal phases of trans-1,3 butadiene probed by FTIR and Raman spectroscopy

In the present work the first spectroscopic data concerning solid butadiene are presented. FTIR and Raman spectra of solid trans-1,3 butadiene in the ordered phase I were recorded at atmospheric pressure down to 12 K. The FTIR technique was used to characterize the phase diagram of butadiene in the 0-7 GPa and 150-300 K pressure-temperature range. Besides phase I another solid phase (phase II), orientationally disordered, was found to be stable at pressures above 0.5 GPa between the liquid and the ordered phase I. A monoclinic C2h5 crystal structure with two molecules per cell sitting on Ci sites is proposed for phase I.