Аннотация
This research reports a pressure dependent Raman study of the sorbic
acid between 0.0 and 10.0 GPa. The unpolarized Raman spectra were
measured in the spectral range of 20-3000 cm(-1). The high-pressure
Raman scattering study of the sorbic acid showed that it underwent a
gradual, disordering process. At the room temperature and at the ambient
pressure conditions, the crystal structure of the sorbic acid belongs to
the monoclinic system with a C2/c (C-2h(6)) space group. The pressure
increase induced a higher disorder in the monoclinic unit cell, since a
single bending mode, and only very broad stretching Raman modes are
present at pressure of similar to 10 GPa. Upon pressure release the
high-pressure phase transforms directly into the ambient-pressure phase.
The presence of the internal vibrational modes is a guarantee that the
molecular structure is maintained. Beyond this, the presence of external
modes shows that the crystal has a memory to reverse the process and
suggest that the crystal, which was in high disorder (broad Raman
bands), does not suffer decomposition in the crystalline structure. The
DFT calculations for the sorbic acid were performed in order to
understand the vibrational properties. The theoretical study showed that
the volume of the unit cell and beta angle decrease significatively when
passing from the 0.0 GPa to 8.0 GPa. The decreases in the volume and
beta angle of this particular unit cell were supposed to induce the
larger increase in the bandwidths of the observed bands, pointing to
some disorder in the monoclinic phase. (C) 2017 Elsevier B.V. All rights
reserved.
Пользователи данного ресурса
Пожалуйста,
войдите в систему, чтобы принять участие в дискуссии (добавить собственные рецензию, или комментарий)