Equation of state, phase stability, and amorphization of SnI[superscript 4] at high pressure and temperature

Abstract

We have measured the pressure-induced amorphization of tin iodide (SnI[superscript 4]) as a function of temperature and found a small (<1 GPa) increase in the initiation pressure of the transition from 293 to 523 K. We have also determined the P-V equation of state while the material undergoes the amorphization, including multiple compressions of a single sample, using a diamond-anvil cell and x-ray diffraction. Apparent stiffening upon multiple compression of the sample can be explained by either an increase in nonhydrostaticity during loading or, possibly, changes in the initial crystal structure upon decompression recrystallization. Contrary to previous interpretations of the amorphization being a two-stage process, with SnI[superscript 4] converting to a second (unidentified) crystalline phase before the loss of Bragg intensities, the present experiments show that it is also possible to amorphize SnI[superscript 4] without the appearance of the second crystalline phase. While the new diffraction peaks appear upon the first compression of a sample, subsequent compressions of the same sample do not show these new peaks; instead, long-range ordering of the original cubic crystal structure is lost.