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

Abstract

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 A1g. 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.