Sean J Gilliam

Bio: Sean J Gilliam is an academic researcher from University of Missouri. The author has contributed to research in topics: Normal mode & Molecular orbital. The author has an hindex of 3, co-authored 3 publications receiving 78 citations.

A theoretical study of As4O6: vibrational analysis, infrared and raman spectra

Abstract: The first complete ab initio theoretical study of tetraarsenic hexoxide (As 4 O 6 ) is reported. The normal mode frequencies, intensities and the corresponding vibrational assignments of As 4 O 6 in T d symmetry were calculated using the gaussian 98 set of quantum chemistry codes at the HF, MP2, and DFT/B3LYP levels of theory using the 6-311G* basis set. By comparison to experimental data deduced by our laboratory and others, correction factors for the calculated vibrational frequencies were determined and compared. Normal modes were decomposed into three non-redundant motions (As–O–As stretch, As–O–As bend, and As–O–As wag). Percent relative errors found for the HF, DFT, and MP2 corrected frequencies when compared to experiment are 3.6, 4.6, and 5.0, respectively. Electron distributions for selected molecular orbitals are also considered.

Uniformly dispersed self-assembled growth of Sb2O3/Sb@graphene nanocomposites on a 3D carbon sheet network for high Na-storage capacity and excellent stability

Abstract: Large volume changes cause a series of complicated problems in alloy-type anodes, such as pulverization, exfoliation and the capacity decay which results. Therefore, solutions for the problems caused by large volume changes in sodium ion battery (SIB) anodes are urgently needed. Herein, we report a novel route to encapsulate Sb2O3/Sb nanoparticles (Sb2O3/Sb-NPs) within a graphene shell nanostructure (Sb2O3/Sb@graphene) via microwave plasma irradiation of Sb(CH3COO)3 and a subsequent graphene growth procedure. The designed structure, Sb2O3/Sb@graphene NPs anchored on carbon sheet networks (CSNs), provides an ultra-thin, flexible graphene shell to accommodate the volume changes of Sb2O3/Sb, and thus demonstrates excellent cycling stability (92.7% of the desodiation capacity was retained after 275 cycles), a long cycle life (more than 330 cycles) and a good rate capability (220.8 mA h g−1 even at 5 A g−1). The stability could be compared to that of commercial graphite in lithium ion batteries.

Electrochemically Synthesized Sb/Sb2O3 Composites as High-Capacity Anode Materials Utilizing a Reversible Conversion Reaction for Na-Ion Batteries

Abstract: Sb/Sb2O3 composites are synthesized by a one-step electrodeposition process from an aqueous electrolytic bath containing a potassium antimony tartrate complex. The synthesis process involves the electrodeposition of Sb simultaneously with the chemical deposition of Sb2O3, which allows for the direct deposition of morula-like Sb/Sb2O3 particles on the current collector without using a binder. Structural characterization confirms that the Sb/Sb2O3 composites are composed of approximately 90 mol % metallic Sb and 10 mol % crystalline Sb2O3. The composite exhibits a high reversible capacity (670 mAh g–1) that is higher than the theoretical capacity of Sb (660 mAh g–1). The high reversible capacity results from the conversion reaction between Na2O and Sb2O3 that occurs additionally to the alloying/dealloying reaction of Sb with Na. Moreover, the Sb/Sb2O3 composite shows excellent cycle performance with 91.8% capacity retention over 100 cycles, and a superior rate capability of 212 mAh g–1 at a high current den...

Electronic Structures of Antimony Oxides

Abstract: This study details density functional theory calculations on all the polymorphs of the binary oxides of antimony (Sb2O3, Sb2O4, and Sb2O5) to assess the electronic structures and differences in bon...

First-Principles Modeling of the “Clean-Up” of Native Oxides during Atomic Layer Deposition onto III–V Substrates

Abstract: The use of III–V materials as the channel in future transistor devices is dependent on removing the deleterious native oxides from their surface before deposition of a gate dielectric. Trimethylaluminium has been found to achieve in situ “clean-up” of the oxides of GaAs and InGaAs before atomic layer deposition (ALD) of alumina. Here we propose seven reaction mechanisms for “clean-up”, featuring exchange of ligands between surface atoms, reduction of arsenic oxide by methyl groups, and desorption of various products. We use first-principles density functional theory (DFT) to determine which mechanistic path is thermodynamically favored. We also discuss the statistical likelihood of the interdependent pathways. “Clean-up” of an oxide film is shown to strongly depend on electropositivity of the precursor metal, affinity of the precursor ligand to the oxide, and the redox character of the oxide. The predominant pathway for a metalloid oxide such as arsenic oxide is reduction, producing volatile molecules or ...