Date of Award

2017-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

Rajendra Zope

Second Advisor

Tunna Baruah

Abstract

We present the most stable structures for VXSc3-XN@C2n (where X=1-3 and 2n=70, 76, 78 and 80) using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search procedure developed involved structural optimizations of thousands of fullerenes and correctly identifies the experimentally observed VSc2N@C80 and V2ScN@C80 isomer as the most stable structures. The structural analysis shows that a few V-doped endohedral fullerenes do not follow the isolated pentagon rule that dictates the stability of fullerenes. The V-doped fullerenes show interesting electronic and magnetic properties. We have also studied the electronic structure studies on C60@C240 onion at the DFT level using all electrons and large polarized Gaussian basis sets. The calculations indicate that the two nested fullerenes are weekly interacting and their electronic structure is essentially unperturbed. From the observed values of electron affinity and ionization potential, it can be inferred that the onion has not only high electron accepting capacity but also is rather stable against oxidation. We also present a density functional study on the structural and electronic properties of Zinc Sulfide cages ZnxSx [x = 12, 16, 24, 28, 36, 48, 108] and an onion-like structure Zn96S96. The study of energetics and stability, performed using large polarized Gaussian basis sets indicated that all structures to be energetically stable with similar binding energy of 5.5 - 5.6 eV per ZnS pair. Further computation of electronic properties showed that these cages have large vertical ionization energies and relatively low electron affinities in the range of 6.8-8.1 eV, and 1.7-3.0 eV, respectively. They have large HOMO-LUMO gaps between 2.5 to 3.3 eV and quasi-particle gaps vary from 6.2 eV for Zn12S12 to 4.19 for Zn108S108. The computed vibrational frequencies for selected cages, i.e. Zn12S12, Zn16S16, Zn28S28 (O, S4, and S8 point groups), and Zn36S36 indicate that these cage structures correspond to local minima on the potential energy surface. Finally, the infrared spectra calculated using large basis sets is also reported.

Language

en

Provenance

Received from ProQuest

File Size

186 pages

File Format

application/pdf

Rights Holder

Shusil Bhusal

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