Effects of Van der Waals Interaction and Hubbard Term Correction on First Principles Calculations of Structural and Lattice Dynamical Properties of AgCl

Structural, dielectric, and lattice dynamical properties of AgCl in the rock-salt structure are studied using density functional theory within generalized gradient approximation(GGA) in Perdew-Burke-Erzhenhof(PBE) parametrization and plane-wave pseudopotential method. The effect of van der Waals interaction (vdW) and Hubbard-U is investigated in detail for the lattice parameters, bulk modulus, dielectric, and phonon properties and compared to available experimental measurements. It is found that, inclusion of vdW interactions together with Hubbard U parameter to the standard GGA-PBE (PBE+vdW+U) improved the agreement with experimental lattice constant and bulk modulus of rock-salt AgCl. Moreover, PBE+vdW+U method is also correctly describes the acoustic and transverse optical (TO) phonon dispersion relation curves. The large underestimation (15%) of GGA-PBE in the longitudinal optical (LO) modes with respect to experiment is also decreased to 5% within the PBE+vdW+U method. This work demonstrates the applicability and accuracy of the van der Waals interaction and Hubbard-U term in predicting the structural, dielectric, and lattice dynamical properties of AgCl in the rock-salt structure.