Effect of chemical and hydrostatic pressures on the structural and mechanical properties of orthorhombic rare-earth [formula omitted

Abstract

The response of structural and mechanical properties under chemical (internal) and hydrostatic (external) pressures in RNiO3 (R = Pr, Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm, Yb, and Lu) orthorhombic structures were investigated using atomistic simulation. A set of interatomic potentials that satisfactorily reproduces their properties was obtained and the transferability of potentials found in the literature was verified. The calculations reveal that the behavior of the lattice parameters and the volume of the unit cell with increasing hydrostatic pressure are in agreement with the data found in related literature. Such agreement is also verified in the evolution of the anisotropy as a function of chemical pressure. The influence of both pressures on the bond lengths (RO, NiO) and the bond angles (NiO1Ni, NiO2Ni) also was investigated. Anomalous behavior was obtained for the mean bonding angle (〈NiONi〉) with hydrostatic pressure, which is argued as related to the low sensitivity of the metal-insulating transition temperature (TMI) for compounds with the smallest R ions. Regarding the mechanical part, the elastic constants, the bulk and the shear moduli were studied. The analysis of these quantities under internal and external pressure also suggests the possibility of a structural phase transition.