Structural phase transition and elastic properties of rare earth nitrides

Abstract

The structural phase transition, elastic and thermal properties of nitrides of lanthanum and ytterbium (REN, RE = La and Yb) under high pressure have been investigated by using two-body interionic potential theory with modified ionic charge (Zme) to include Coulomb screening effect by the delocalized f electrons of rare earth ion. The present theoretical approach predicted that LaN and YbN exhibit a NaCl (B1) type structure at an ambient pressure, undergo a structural phase transition from NaCl (B1) into CsCl (B2) phase at 100 GPa and 133 GPa, respectively. We have reported the second order elastic constants (SOECs), third order elastic constants (TOECs) and pressure derivatives of second order elastic constant for these compounds. The variation of elastic constants (C11, C44) with pressure is also presented. The thermal properties and its variation with pressure have been reported for these compounds for the first time.