Pressure-Induced Structural Phase Transitions in the Chromium Spinel LiInCr4O8 with Breathing Pyrochlore Lattice

This study reports high-pressure structural and spectroscopic studies on polycrystalline cubic chromium spinel compound LiInCr4O8. According to pressure-dependent X-ray diffraction measurements, three structural phase transitions occur at similar to 14 GPa, similar to 19 GPa, and similar to 36 GPa. The first high-pressure phase is indexed to the low-temperature tetragonal phase of the system which coexists with the ambient phase before transforming to the second high-pressure phase at similar to 19 GPa. The pressure-dependent Raman and infrared spectroscopic measurements show a blue-shift of the phonon modes and the crystal field excitations and an increase in the bandgap under compression. During pressure release, the sample reverts to its ambient cubic phase, even after undergoing multiple structural transitions at high pressures. The experimental findings are compared to the results of first principles based structural and phonon calculations.

Automated summary

This study investigates the high-pressure behavior of LiInCr4O8 spinel compound using structural and spectroscopic techniques. It reveals three structural phase transitions at approximately 14 GPa, 19 GPa, and 36 GPa, with the first high-pressure phase coexisting with the ambient phase before transforming to the second phase. The spectroscopic measurements show a blue-shift in phonon modes and crystal field excitations, as well as an increase in the bandgap under compression. The experimental findings are compared to first principles calculations.