High-Pressure Phase Transitions and Mechanisms in Lanthanum Mononitride

Abstract A longstanding discrepancy between theoretical predictions and experimental observations on the high-pressure structural transformations of lanthanum mononitride (LaN) has posed challenges for understanding the behavior of heavy transition metal mononitrides. Here, we systematically investigate the structural evolution of LaN under high pressure using first-principles calculations combined with angle-dispersive synchrotron X-ray diffraction, identifying the phase transition sequence and corresponding phase boundaries. Analyses of energetics, kinetic barriers, and lattice dynamics reveal distinct mechanisms driving these transitions. These results clarify the structural stability of LaN and offer guidance for studying other heavy transition metal mononitrides with complex electronic behavior under extreme conditions.