Ab Initio Calculations of Phase Stability in the N–H System at Pressures up to 1.5 TPa

The stability of compounds in the N–H system at 0 K to pressures of 1.5 TPa has been calculated. The evolutionary search for stable structures in the USPEX program has been carried out using the PBEsol + vdW method within the density functional theory. New stable structures in the NH and N3H10 compounds have been discovered and the boundaries of phase transitions in the N3H7, NH3, and NH4 compounds have been refined. At a maximum pressure of 1.5 TPa, stable phases are NH with the P4122 and P4322 structures and NH4 with the C2/c structure. The obtained data can be used for the subsequent calculation of the equations of state of the phases of the N–H system, which is important for planetary physics.