Periodic Trends in the Electronic and Magnetic Structure of Superatomic 3d Transition Metal Chalcogenide Clusters

Author

Gabriel Bohannon, Virginia Commonwealth UniversityFollow

DOI

https://doi.org/10.25772/DW7B-1403

Defense Date

2025

Document Type

Thesis

Degree Name

Master of Science

Department

Physics and Applied Physics

First Advisor

Arthur Reber

Abstract

We have systematically investigated the electronic structure of octahedral transition metal chalcogenide clusters, TM₆S₈(CO)₆, in which the transition metal atoms are from the 3d series in order to identify if periodic properties emerge. We were motivated by the identification of closed electronic shells with electron counts of 96, 100 and 114 in similar clusters from the 4d and 5d transition metal series. Further motivation was the finding of a dual-shell closing in the Fe₆S₈(CN)₆^5- cluster. This cluster is stabilized with a large spin magnetic moment due to the filling of different shells in both the spin up and spin down channels. Normally, 3d transition metal atoms have local spin magnetic moments that are not quenched, so the formation of closed electronic shells with large HOMO-LUMO gap energies does not occur. Clusters with closed electronic shells exhibit enhanced chemical and energetic stability, and clusters with nearby closed electronic shells may behave as superatoms in which their properties are determined by the energy gained by closing that electronic shell. To identify if periodic properties are emerging we have calculated the ground state electronic structure of the TM₆S₈(CO)₆ clusters starting from V₂Cr₄S₈(CO)₆ and ending with Ni₆S₈(CO)₆ using density functional theory. The valence count was controlled by successively exchanging each transition metal atom with the next higher atomic number transition metal. In total, the 27 clusters with valence electron counts ranging from 94 to 120 were studied. The HOMO-LUMO gap, atomization energy, ligand binding energy, ionization energy, and electron affinity were calculated to identify which electron counts correspond to magic numbers. The electron counts of 96, 100, 107, and 114 were identified to behave as having magic numbers, with closed electronic shells at 96, 100, and 114, and a dual electronic shell closure at 107 corresponding to a high spin state of 7 μ_B. Further, the periodic behavior of the clusters with electron counts near 107 behave in a similar way as Hund’s rules with the systematic filling of the spin down shell as the electron count goes from 107 to 114.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-1-2025