Browsing by Author "Musfeldt, Janice L"

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    Chemical bonding and Born charge in 1T-HfS2
    (2021-04-09) Neal, Sabine N; Li, Shutong; Birol, Turan; Musfeldt, Janice L; li000269@umn.edu; Li, Shutong
    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.
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    Raman spectroscopy data and phonon calculations for ScV6Sn6 in P6/mmm and R-3m structures, 2023
    (2023-06-27) Ritz, Ethan T; Birol, Turan; Gu, Yanhong; Musfeldt, Janice L; eritz@umn.edu; Ritz, Ethan T; Birol Research Group, University of Minnesota; Musfeldt Group, University of Tennessee Knoxville
    We use density functional theory (DFT) to calculate the phonon frequencies and the distortions associated with them in the compound ScV6Sn6 in the P6/mmm and R-3m space groups, then compute the overlap between the Raman-active phonons in each structure. This data includes scripts to generate the DFT submission files, the results of those simulations, as well as MATLAB scripts to plot the results. We also include experimental Raman spectroscopy data at temperatures from 5.5 K to 300 K.