High‐pressure micro‐Raman spectra of potassium hexabromostannate(IV), K₂SnBr₆

Abstract

High-pressure micro-Raman spectra of crystalline K,SnBr, were measured at ambient temperature up to 50 kbar using a diamond-anvil cell. A pressure-induced phase transition occurs at cu. 19 kbar. All the observed bands show blue shifts with pressure. The Griineisen parameters (calculated from the pressure coefficients) for the highpressure phase are smaller than thase for the ambient temperaturelpressure monoclinic phase, indicating that the high-pressure phase is denser and less compressible than the monoclinic phase.

A high-pressure synchrotron X-ray powder diffraction study of K2SnBr6

“…The phase transition that we have observed with increase of pressure is undoubtedly the same as that found by Butler and Huang (1990), but the x-ray method allowed identification of the new phase, and is also more sensitive to the onset of the transition.…”

“…Combining OUT new results with those of Swanson (1978) and Butler and Huang (1990) yields the phase diagram of figure 3. The volume compressibility is 1.23 X kbar-I, and there is a 12.76% volume decrease at the phase change, allowing for the cell doubling.…”

“…The title compound has also been studied using vibrational spectroscopy, most recently by Butler and Huang (1990) who reviewed earlier work. Theirs is the fast highpressure investigation.…”

Alkali Tin Halides: Exploring the Local Structure of A2SnX6 (A = K, Rb; X = Cl, Br, I) Compounds Using Solid-State NMR and DFT Computations

“…The cell parameters for K 2 SnBr 6 (space group = P 2 1 / n ) are a = 10.621(2), b = 7.427(2), c = 7.442(2) Å, and β = 90.18(2)° . The small deviation of β from 90° has resulted in K 2 SnBr 6 being called “pseudo-cubic” or “pseudo-tetragonal”. ,, For Rb 2 SnI 6 (space group = P 4/ mnc ), the cell parameters are a = b = 8.0706 Å and c = 11.7650 Å . Despite past theoretical work predicting K 2 SnI 6 , we were unable to synthesize this material using mechanochemical synthesis or solvent-assisted methods.…”

“…However, it is yet to be demonstrated experimentally. While the average long-range structures of A 2 SnX 6 materials are known from diffraction techniques, ,− solid-state nuclear magnetic resonance (NMR) spectroscopy, a complementary method that can be used to study local structure and dynamics, ,,− is nearly absent from their suite of characterizations . Only recently has NMR spectroscopy been used to investigate Cs 2 SnX 6 , revealing important information about octahedral lattice dynamics, which is a property known to influence the optoelectronic properties of these materials. , …”