Raman spectra of crystalline antimony triiodide and arsenic triiodide

Abstract

Raman spectra of single crystals of the layered compounds SbI, and AsI, at 15K are reported. Polarization measurements allow the eight principal peaks to be classified according to symmetry species. Results of a group theoretical analysis based on both molecular and ionic descriptions of the crystal structure are discussed, and assignments of the observed spectra are proposed. Some ramifications of the more ionic nature of SbI, on its spectrum are briefly described.

Raman Scattering under Hydrostatic Pressures in Layered BiI3 and SbI3 Crystals

“…For instance, Kiefer [2] investigated the Raman spectra of BiI 3 , SbI 3 , and AsI 3 at room temperature and made assignments of the modes. Later, Anderson et al [3] obtained Raman spectra of SbI 3 and AsI 3 at 15 K. This paper is the first to report the Raman modes of BiI 3 , SbI 3 at pressures up to 2 GPa. We argue that the bonding in SbI 3 becomes the same as that in BiI 3 above 0.9 GPa; a similar change in bonding had previously been argued for AsI 3 , which has a similar structure to SbI 3 , at about 4.5 GPa [4].…”

“…The luminescence is due to certain stacking faults, and the peak of the luminescence band shifts to lower frequencies with increasing pressure [10]. In layered crystals such as BiI 3 and SbI 3 , the bonding is strongly anisotropic. Therefore, when hydrostatic pressure is applied to BiI 3 crystals, stacking faults can form by the slipping of layers at some structural imperfection sites such as grain boundaries, dislocations, and vacancies.…”

“…The observable first-order scattering lines of the Raman active modes are determined by the symmetry of the Raman tensors and the geometry of the experimental configuration [1]. The assignments of the observed Raman spectra of BiI 3 and SbI 3 have been reported by several workers [2,3]. For instance, Kiefer [2] investigated the Raman spectra of BiI 3 , SbI 3 , and AsI 3 at room temperature and made assignments of the modes.…”

“…BiI 3 and SbI 3 crystals consist of sequentially stacked unit layers, with each layer ordered as I-metal-I along the c-axis. Each layer is tightly held together by strong covalent-ionic bonds, but the weak interlayer forces between neighboring atomic sheets of iodine are thought to be van der Waals forces.…”

Vibrational spectra of arsenic triiodide: a lattice dynamics study

“…A correlation diagram, linking the symmetry species for the free molecule, the site and the unit cell, has been published previously. 5 The four internal molecular normal modes, two totally symmetric and two doubly degenerate, are each split into two components as a result of coupling in the unit cell, with one component Raman active and the other infrared active. There are also four librations (hindered rotations), two active in each type of spectrum, two optical translational modes, which are Raman active only, and two acoustic modes, which have zero wavenumber at the Brillouin zone centre.…”