The coupling of lattice-strain and phonon induced order-disorder phase transition in layered LiGaO2

Highlights: • The large-size crystal of α-LiGaO₂ was synthesized at high pressure 5 GPa and high temperature 1873 K. • We observed a pressure-induced order-disorder phase transition in α-LiGaO₂ at about 16 GPa via in situ experiments. • The phase transition occurs based on coherent nucleation induced by anisotropic compression. • The coupling of lattice strain and phonon mode A_1g is the atomic mechanism that governs this phase transition. Recently, order-disorder phase transition has been considered as an emerging method to engineer bandgap in semiconductors. In this work, we uncovered that the coupling of lattice strain and phonon dominates the pressure-induced order-disorder phase transition in α-LiGaO₂ via in situ high-pressure angle dispersive X-ray diffraction (ADXRD) and Raman scattering experiments, with the aids of first-principles calculations. Upon compression, ADXRD experiments show that the anisotropic compression of the layered structure leads to the order-disorder phase transition. Combining with lattice dynamics, we observed that the transition begins at about 16 GPa based on coherent nucleation induced by the oxygen atoms opposite motion that is the result of the coupling of lattice strain and phonon mode A_1g. This result further shows that the disorder in crystal can be a correlated behavior and controlling the disorder in crystal can be used to create materials with new or improved functionality.