Structure–Property Correlation Studies of Potassium 4,4′-Bis(dinitromethyl)-3,3′-azofurazanate: A Noncentrosymmetric Primary Explosive

Abstract

The knowledge of mechanical, vibrational, electronic properties, and origin of polarizability of a noncentrosymmetric explosive materials plays a crucial role in understanding the phase transition mechanism and stand-off detection of high energy material (HEM) residues on the surfaces and interfaces. In the present study, we have explored the role of crystal structure and chemical composition in predicting the structural, dynamical, electronic, and optical properties of two newly synthesized noncentrosymmetric green primary explosives, potassium 4,4′-bis(dinitromethyl)-3,3′-azofurazanate (K 2 BDAF) and potassium 1,1′-dinitramino-5,5′-bistetrazolate (K 2 DNABT), using density functional theory simulations. The calculated structural and mechanical properties suggest that K 2 BDAF and K 2 DNABT are mechanically stable and possess lower bulk modulus values [K 2 BDAF (18.91 GPa) < K 2 DNABT (22.4 GPa)] than toxic lead azide Pb(N 3 ) 2 (26 GPa). The Born effective charge (BEC) and vibrational, thermodynamic, and phonon dispersion studies reveals that both crystals are dynamically stable and that K 2 BDAF is found to be more stable, more polarizable, and easily detectable than K 2 DNABT. The TB-mBJ electronic band structure study reveals that K 2 BDAF is an indirect band gap (along R → V high symmetry points) material with a gap of 2.37 eV < K 2 DNABT (3.57 eV, direct). The density of states and charge density plots show that both crystals possess mixed covalent and ionic bonding nature, and these results are consistent with BEC analysis. The nitrogen, oxygen and carbon p states are found to be dominant near the Fermi level in the valence band. From the optical properties study, it is found that the studied explosive materials have the lowest dielectric constant compared with the well-known 4-N,N-dimethylamino-4-N-methylstilbazolium tosylate (DAST) crystal, i.e., K 2 DNABT (2.68) < K 2 BDAF (2.91) < DAST (5.2), and show birefringence similar to (K 2 BDAF static value, 0.32; at 532 nm, 0.58), (K 2 DNABT static value, 0.25; at 532 nm, 0.27) that of DAST (0.39, 0.55, 0.64) and 4-N,Ndimethylamino-4′-N′-methylstilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) (0.45, 0.63) NLO crystals. For both the studied explosives, the absorption is found to be strong in the [010] direction and follows the relation α(K 2 BDAF) < α(K 2 DNABT). The analysis of differences in BEC reveals that from K 2 DNABT to K 2 BDAF, the positive contribution of atoms to total birefringence increases as follows: K1 (0.09559), O1 (0.69236), O2 (0.77962), N1 (1.41018), N2 (0.92394), N3 (0.27415), N4 (0.74264), and N5 (0.84502). The negative contribution from C1 is increased by −1.29582. Over all, our results are in agreement with the experimentally reported sensitivity trend, and the reasons behind the sensitivity differences of K 2 DNABT and K 2 BDAF are explored.

Growth of 4-N,N-Dimethylamino-4'-N'-methyl-stilbazolium Tosylate (DAST) Organic Single Crystals Controlled by Oleic Acid

“…Figure 7b shows the plot of (αhν) 2 versus hν for both the DAST single crystals. The value of the Tauc optical band gap was estimated to be 2.33 eV for the DAST crystal grown without the OA control (Figure 7b), agreeing well with those previously reported [24,25]. It should be noted that a higher E g of 2.43 eV was measured from the DAST crystal grown under the control of the OA (Figure 7b).…”

Trinitromethyl-triazolone (TNMTO): a highly dense oxidizer

“…1 and 5.d Ref. 16.e Ref. 17.fMolecular formula.gFormula weight.hOxygen balance (based on CO).iOxygen balance (based on CO 2 ).jOxygen content in %.kNitrogen and oxygen contents in %.lCalculated enthalpy of formation.mMeasured densities, gas pycnometer at 25 °C.nThermal decomposition temperature (onset) under nitrogen gas (DSC, 5 °C min −1 ).oCalculated detonation velocity.pCalculated detonation pressure.qHeat of detonation.rImpact sensitivity.sFriction sensitivity.tBond dissociation energies of trigger bond.u Φ H–L = HOMO–LUMO energy gaps.v I sp = specific impulse of neat compound.w ρI sp = density specific impulse of neat compound.xCharacteristic velocity.y I sp = specific impulse at 88% compound and 12% Al.z ρI sp = density specific impulse at 88% compound and 12% Al.aaSpecific impulse were calculated at ambient pressure of 0.1 MPa, chamber pressure of 7 MPa, an isobaric pressure of 70 bar and initial temperature of 3300 K.abThis work.…”

Pressure, directional dependent mechanical anisotropies and phase transition studies of β-5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) and 2,4,6-triamino-1,3,5-trinitrobenzene (TATB)

“…We have calculated all these parameters by using the obtained single crystal elastic constants with Voigt's, Reuss's and Hill's approximations [23][24][25][26][27][28][29] and the corresponding equations used for the estimation are listed below. (21.174 GPa, 1.435 GPa).…”

“…The results of A C , A U at 0 GPa of NTO (0.5, 11.02), TATB (0.6, 15.43) indicates that, TATB may possess large mechanical anisotropy. We further calculated the Debye temperature θ D values of NTO and TATB using the elastic wave mean velocities (V m ), longitudinal (V l ), transverse (V t ) velocities using the following equations [23][24][25][26][27][28][29]:…”