Higher-order elastic constants of La1.84Sr0.16CuO4 high-temperature superconductor

Finite deformation theory is used to obtain the strain energy density ϕ of a tetragonal 2-1-4-type single crystal of the high-temperature superconductor La2−xSrxCuO4. The complete set of second and third-order elastic constants of the high-temperature superconductor La2−xSrxCuO4 (x = 0.16) is calculated by taking into account the interactions between nine nearest-neighbour atoms in the lattice and using Mie-Grüneisen interatomic potential. For the sake of comparison we have also computed the values of these constants for x = 0.13-0.20. The values of third-order elastic constants of La2−xSrxCuO4 (x = 0.13-0.20) are negative and their absolute magnitudes are one order higher than those of the second-order elastic constants.