Ab Initio study on structural, electronic, magnetic and dielectric properties of LSNO within Density Functional Perturbation Theory

LSNO (La$_{\mathrm{2-x}}$Sr$_{\mathrm{x}}$NiO$_{\mathrm{4}})$ is of great interest due to its colossal dielectric constant (CDC) and rich underlying physics. While being an antiferromagnetic insulator, localized holes are present in the form of stripes in the Ni-O planes which are commensurate with the inverse of the Sr concentration. The stripes are a manifestation of charge density waves with period approximately 1/x and spin density waves with period approximately 2/x. Here, the spin ground state is calculated via LSDA $+$ U with the PAW method implemented in VASP. Crystal structure and the effective Hubbard U parameter are optimized before calculating $\varepsilon_{\mathrm{\infty }}$ within the independent particle approximation. $\varepsilon_{\mathrm{\infty }}$ and the full static dielectric constant (including the lattice polarizability) $\varepsilon _{\mathrm{0}}$ are calculated within Density Functional Perturbation Theory.