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Miller M.,Armament Research Development and Engineering Center | Owens F.J.,York College - The City University of New York
Chemical Physics | Year: 2012

Density functional theory is used to calculate the bond dissociation energy to cleave the C 60C 60 bond of the paramagnetic X-C 60C 60-X and X-C 60C 60 dimers where X is F, OH, O and H. The results show that these dimers would not be stable much above room temperature and therefore cannot constitute the paramagnetic phase needed to form the observed ferromagnetism which has been shown to be stable up to 800 K. The calculated bond dissociation energies to remove an F, OH or H from a single C 60 are large suggesting that they could be the source of the unpaired spin needed for the high temperature ferromagnetism. © 2011 Elsevier B.V. All rights reserved. Source


Miller M.,Armament Research Development and Engineering Center | Owens F.J.,York College - The City University of New York
Solid State Communications | Year: 2011

Density Functional Theory is used to investigate the effect of altering the B/N ratio and carbon doping on the electronic and magnetic structure of zigzag, (7, 0) and armchair (5, 5) boron nitride nanotubes. The calculations indicate that increasing the boron content relative to the nitrogen content significantly reduces the band gap to a value typical of a semiconductor. Calculations of carbon doped semiconducting BN tubes, which have more boron atoms than nitrogen atoms have a net spin and a difference in the density of states at the valence band between the spin up and spin down state. © 2011 Elsevier Ltd. All rights reserved. Source


Puszynski J.A.,South Dakota School of Mines and Technology | Bulian C.J.,South Dakota School of Mines and Technology | Swiatkiewicz J.J.,South Dakota School of Mines and Technology | Kapoor D.,Armament Research Development and Engineering Center
International Journal of Energetic Materials and Chemical Propulsion | Year: 2012

Consolidated nanothermite felts with reduced sensitivity to electrostatic discharge for safer handling were produced without a significant reduction of the nanothermite reactivity. A polyester felt material with a thickness of 1.65 mm was easily infiltrated with a nanothermite slurry and the dried felt material prevented small particles from breaking off during handling. Combustion of 100 mg of the dried felt nanothermite in a closed-volume pressure cell generated higher pressure than those generated by nanothermite granules produced using a similar water-based processing method. The nanothermite felts also effectively absorbed nitrocellulose as a gasifying agent without a significant decrease in reaction rate. High-density reactive composites, based on tantalum metal fuel with a specific gravity of 16.6 and nanoscale Bi2O3 oxidizer, were formed with densities in excess of 5.0 g/cm3. THV 220A, a fluorocarbon polymer with oxidizing properties, was used as an effective binder in the composite. These materials were combined in acetone with tetrafluoroethylene, hexafluoropropylene, and vinylidene (THV), and after drying were pressed into pellets. Combustion of an 800-mg pellet lasted 5 s and was accompanied by the formation and ejection of hot particles from the surface of the pellet. Differential scanning calorimetry analysis determined that the ignition of the high-density composite occurs below 620 K, which is lower than common in nanothermite systems. © 2012 by Begell House, Inc. Source


Miller M.,Armament Research Development and Engineering Center | Owens F.J.,York College - The City University of New York
Computational and Theoretical Chemistry | Year: 2012

Because thermally induced exothermic reactions in energetic molecules occur in the melt, theoretical calculations of initial reaction steps should be modeled in the liquid phase. Here we present a first attempt to address this problem by calculating bond dissociation energies for the initial step in the molten phase of energetic materials employing density functional theory and the self consistent reaction field model of the liquid state. The bond dissociation energies for removal of NO 2 from a number of energetic molecules are calculated using the same basis set in the gas and the liquid enabling comparison of results. © 2012 Elsevier B.V. Source


Miller M.,Armament Research Development and Engineering Center | Owens F.J.,City College of New York
Chemical Physics | Year: 2011

The possibility of stable two dimensional armchair and zigzag silicon nanoribbons having the same structure as graphene is examined using Density Functional Theory (DFT). The calculations predict that armchair Si ribbons, but not zigzag ribbons, are stable two dimensional structures. The electronic and magnetic properties of undoped and hole and electron doped armchair Si ribbons are calculated. It is predicted that electron and hole doped Si armchair ribbons have the potential to be ferromagnetic semiconductors. Copyright © 2011 Published by Elsevier B.V. All rights reserved. Source

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