Chemical bonding and Born charge in 1T-HfS2

Abstract: We combine infrared absorption and Raman scattering spectroscopies to explore the properties of 1T-HfS2- a heavy transition metal chalcogenide with strong spin-orbit coupling due to incorporation of the 5d center. We employ the LO-TO splitting of the Eu mode along with a reevaluation of mode mass, unit cell volume, and dielectric constant to reveal the Born effective charge. We find ZB*= 5.33e, in excellent agreement with complementary first principles calculations. In addition to resolving controversy over the nature of chemical bonding in this system, we decompose the Born charge into polarizability and local (ionic) charge. We find α= 5.07 Å3 and Z*= 5.19e, respectively. In order to understand how ZB* relates to the nominal 4+ charge of the Hf center, we decompose the theoretical Born effective charge into band-by-band contributions, and find that polar displacement-induced charge transfer from sulfur p to hafnium d orbitals is responsible for the enhancement of Born charge. 1T-HfS2 is thus an ionic crystal with strong and dynamic covalent effects.

Description
Two main parts of simulations are included in this dataset: 1. Density functional theory: the input and output for Vienna Ab-initio Simulation Package (VASP) used in this publication, which include: POSCAR: Crystal structure files. INCAR: Input parameters. KPOINTS: Input parameters (for k-mesh). VASPRUN.XML: A formatted output. 2. Wannier function: the input and output for Wannier90, which includes: wannier90.win: Input parameters. wannier90.wout: A formatted output.