The Musfeldt Group published their work “Chemical bonding and Born charge in 1T-HfS2” in npj 2D Materials and Applications. This is a collaborative research with the Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN.
Their research combines infrared absorption and Raman scattering spectroscopies to explore the properties of the heavy transition metal dichalcogenide 1T-HfS2. They employ the LO–TO splitting of the Eu vibrational mode along with a reevaluation of mode mass, unit cell volume, and dielectric constant to reveal the Born effective charge.
In addition to resolving the controversy over the nature of chemical bonding in this system, we decompose Born charge into polarizability and local charge. Polar displacement-induced charge transfer from sulfur p to hafnium d is responsible for the enhanced Born charge compared to the nominal 4+ in hafnium. 1T-HfS2 is thus an ionic crystal with strong and dynamic covalent effects.
This work places the vibrational properties of 1T-HfS2 on a firm foundation and opens the door to understanding the properties of tubes and sheets.