Michigan Technological University
Department of Physics

is pleased to announce the

Graduate Students Series Spring 2004

S. Gowtham

Physics Graduate Student
Michigan Technological University
Advisor: Dr. Ravindra Pandey

Neutral And Anionic Al₃O_n (n = 6 - 8) Clusters

Results of a combined theoretical and experimental study of neutral and anionic Al₃O_n (n
= 6 - 8) will be discussed in this talk. The results are based on Density Functional Theory (DFT)
calculations and the focus is mainly on the structural and electronic properties. Results reveal
that sequential oxidation of Al₃O₅ induces significant structural changes in cluster
configurations. Electronic properties of these clusters appear to be approaching the bulk
properties. The hydration behavior of n = 6 cluster was experimentally examined using Ion Trap
- Secondary Ion Mass Spectrometer (IT-SIMS) under vacuum conditions and the result obtained
is consistent with our calculation.

Kah Chun Lau

Physics Graduate Student
Michigan Technological University
Advisor: Dr. Ravindra Pandey

Equilibrium Geometry and
Electron Detachment Energies of
Anionic Cr₂O₄, Cr₂O₅ and Cr₂O₆ Clusters

Theoretical calculations based on density functional theory are performed to identify the
lowest-energy geometries, ground-state spin multiplicities, and vertical electron detachment
energies of negatively-charged Cr₂O_n (n=4-6) clusters. The sequential oxidation of the
dichromium oxide clusters tends to quench the spin configuration of the ground state which is
attributed to the interplay between nonbonding 3d_Cr and bonding 3dCr-2p_O
molecular orbitals in the given cluster. For Cr₂O₆^-, the bonding orbitals
dominate the higher valence molecular orbitals
leading to a very high value of electron detachment energy for the cluster. Calculations also find
the symmetric and asymmetric stretching of the terminal Cr-O bonds to be associated with the
high frequency region of the vibrational spectrum of these clusters. Analysis of Mulliken charges
and atomic spin density reveals two Cr atoms to be chemically equivalent but magnetically
inequivalent atoms in these anionic clusters.

Thursday, April 1, 2004

4:00 p.m., Fisher 139

Refreshments will be served

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