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Stephen A.D.,Periyar University | Kumaradhas P.,Periyar University | Pawar R.B.,High Energy Material Research Laboratory
Propellants, Explosives, Pyrotechnics | Year: 2011

A quantum chemical calculation and a charge density analysis have been performed on the energetic molecule trinitrobenzene (TNB) to characterize its bond strength and to relate the bond topological parameters with the impact sensitivity. The optimized geometry of the molecule was calculated by the density functional method B3P86 with the basis set 6-311G. The bond topological analysis predicts a significantly low bond electron density (∼1770 e nm -3) as well as Laplacian of electron density (-1.67 ×10 6 e nm -5) for C-N bonds. This low value of the Laplacian indicates, the charges of these bonds are highly depleted, which confirms that these are the weakest bonds in the molecule. The N=O bonds bear a high negative value of Laplacian, reflecting that the bond charges are highly concentrated. The isosurface of the molecular, electrostatic potential (ESP) shows large electronegative regions at the vicinity of -NO 2 groups. Further analysis of ESP in the bonding region allows predicting the impact sensitivity. A sound relationship has been found between the ESP at the mid point of the bonds and its bond charge depletion. The positive ESP at the mid points of highly charge depleted C-NO 2 bonds reveals that these bonds are the sensitive bonds in the molecule. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stephen A.D.,Periyar University | Pawar R.B.,High Energy Material Research Laboratory | Kumaradhas P.,Periyar University
Journal of Molecular Structure: THEOCHEM | Year: 2010

To understand the energetic properties of 2,3,4-Trinitrotolune (TNT) molecule, a quantum chemical calculation and the electronic charge density analysis have been performed. The density functional theory (B3P86/6-311G**) calculation was carried out using Gaussian03 software. The energy-minimized wave function obtained from DFT was used for the charge density analysis. The inductive and steric effects of methyl and nitro substituents are not showing any unique geometric and bond topological features on C-C bonds of phenyl ring. A large charge accumulation (∼3.49eÅ-3) is found in NO bonds; its corresponding Laplacian of electron density is ∼-27.6eÅ-5, this indicates that the charges of the bonds are highly concentrated. Comparatively, the Laplacian of electron density of C-NO2 (∼-17.1eÅ-5) and C-CH3 (-14.7eÅ-5) bonds are found very less, confirm that the bond charges are significantly depleted; hence these bonds are considered as the weak bonds in the molecule. The isosurface of electrostatic potential of the molecule displays high electronegative region around the nitro groups, which are the reaction surface of the molecule. Present study predicts the relationship between the bond charge depletion and the bond sensitivity. Further, it proposes that, if the highly charge depleted bonds exhibit positive Vmid values, which are the sensitive bonds. We found, C-N bonds are the sensitive bonds in the molecule. © 2010 Elsevier B.V.

Leela Ch.,University of Hyderabad | Venkateshwarlu P.,University of Hyderabad | Singh R.V.,High Energy Material Research Laboratory | Verma P.,High Energy Material Research Laboratory | Prem Kiran P.,University of Hyderabad
Optics Express | Year: 2014

Laser ablated shock waves from compacted metal nanoenergetic powders of Aluminum (Al), Nickel coated Aluminum (Ni-Al) was characterized using shadowgraphy technique and compared with that from Boron Potassium Nitrate (BKN), Ammonium Perchlorate (AP) and Potassium Bromide (KBr) powders. Ablation is created by focused second harmonic (532 nm, 7 ns) of Nd:YAG laser. Time resolved shadowgraphs of propagating shock front and contact front revealed dynamics and the precise time of energy release of materials under extreme ablative pressures. Among the different compacted materials studied, Al nanopowders have maximum shock velocity and pressure behind the shock front compared to others. © 2014 Optical Society of America.

Srinivasan P.,Periyar University | Asthana S.N.,High Energy Material Research Laboratory | Pawar R.B.,High Energy Material Research Laboratory | Kumaradhas P.,Periyar University
Structural Chemistry | Year: 2011

The bond topological and electrostatic properties of nitrogen-rich 4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole (TNBI) energetic molecule have been calculated from the DFT method with the basis set 6-311G** and the AIM theory. The optimized geometry of this molecule is almost matched with the experimental geometric parameters. The electron density at the bond critical point and the Laplacian of electron density of C-NO 2 bonds are not equal, one of them is much weaker than the other. Similar trend exists in the C-N bonds of the imidazole ring of the molecule. The ratio of the bond dissociation energy (BDE) of the weakest bond to the molecular total energy exhibits nearly a linear correlation with the impact sensitivity; its h 50% value is ∼32.01 cm. The electrostatic potential around both the nitro groups are found unequal; the NO 2 group of weakest C-NO 2 bond exhibits an extended electronegative region. © 2011 Springer Science+Business Media, LLC.

Dey A.,High Energy Material Research Laboratory | Nangare V.,High Energy Material Research Laboratory | More P.V.,University of Pune | Shafeeuulla Khan M.A.,High Energy Material Research Laboratory | And 3 more authors.
RSC Advances | Year: 2015

A green process was developed for a graphene-titanium dioxide nanocomposite (GTNC) synthesis by dispersing titanium dioxide (TiO2) nanoparticles and graphene nano-sheets (GNSs) in ethanol via ultrasonication followed by microwave irradiation. The synthesized GTNC was well characterized by various tools: viz. XRD, HRTEM, FTIR and Raman spectroscopy. Also, Simultaneous Thermal Analysis (STA) and Differential Scanning Calorimetry (DSC) techniques have been employed to study the enhancement of the catalytic activity of the GTNC for the decomposition of Ammonium perchlroate (AP). The GTNC with 5 wt% in AP was found to be a highly effective catalyst for the AP decomposition. The decomposition temperature decreases from 412.87°C to 372.50°C and ΔH increases from 2053 to 3903 J g-1. Furthermore, the GTNC was identified as an effective burn rate enhancer (i.e. combustion catalyst) for an AP based composite propellant for solid rocket propellants as confirmed by STA, DSC, activation energy calculations and burn rate measurements. The results show that the burn rate of the propellant increases by 24% for the TiO2 nanoparticle based composition compared to the base composition, whereas a significant increase of 50% is achieved in the presence of the GTNC. Hence, the performance is improved significantly for the solid rocket propellant. © The Royal Society of Chemistry 2015.

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