Atomistic Modeling of Anisotropic Mechanical Properties of Lanthanum Zirconate Nanocystal

Lanthanum zirconate (La2Zr2O7, or LZ) has been widely recognized as a promising candidate material for thermal barrier coating (TBC) applications since it has low thermal conductivity, high-temperature phase stability, and low sintering activity. However, the mechanical properties of LZ crystal have not been fully understood, which hinders it from future applications. In this work, atomistic simulations were performed to study the anisotropic mechanical properties of LZ crystal. Using both the first principles and molecular dynamics (MD) calculations, uniaxial tensile tests of LZ crystal in [001], [011], and [111] directions were simulated. The stress-strain curves of the tensile tests were calculated, and the ultimate tensile strength and toughness were derived. The Young's moduli in [001], [011], and [111] directions were calculated using both the stress-strain curves and an analytical method for small deformation. Additionally, shear stress-strain curves in {111} and {111} directions were investigated using both the first principles calculations and the MD method. Results show that Young's modulus of LZ crystal is highly anisotropic. The crystal has the highest Young's modulus in [111] direction, and {111} direction is the favorable slip system during shear deformations