Why are [P(C6H5)4](+)N3- and [As(C6H5)4](+)N3- ionic salts and Sb(C6H5)4N3 and Bi(C6H5)4N3 covalent solids? A theoretical study provides an unexpected answer

A recent crystallographic study has shown that, in the solid state, P(C(6)H(5))(4)N(3) and As(C(6)H(5))(4)N(3) have ionic [M(C(6)H(5))(4)](+)N(3)(-)-type structures, whereas Sb(C(6)H(5))(4)N(3) exists as a pentacoordinated covalent solid. Using the results from density functional theory, lattice energy (VBT) calculations, sublimation energy estimates, and Born-Fajans-Haber cycles, it is shown that the maximum coordination numbers of the central atom M, the lattice energies of the ionic solids, and the sublimation energies of the covalent solids have no or little influence on the nature of the solids. Unexpectedly, the main factor determining whether the covalent or ionic structures are energetically favored is the first ionization potential of [M(C(6)H(5))(4)]. The calculations show that at ambient temperature the ionic structure is favored for P(C(6)H(5))(4)N(3) and the covalent structures are favored for Sb(C(6)H(5))(4)N(3) and Bi(C(6)H(5))(4)N(3), while As(C(6)H(5))(4)N(3) presents a borderline case.     

Pentazole-based energetic ionic liquids: a computational study

The structures of protonated pentazole cations (RN5H+), oxygen-containing anions such as N(NO2)2-, NO3-, and ClO4- and the corresponding ion pairs are investigated by ab initio quantum chemistry calculations. The stability of the pentazole cation is explored by examining the decomposition pathways of several monosubstituted cations (RN5H+) to yield N2 and the corresponding azidinium cation. The heats of formation of these cations, which are based on isodesmic (bond-type conserving) reactions, are calculated. The proton-transfer reaction from the cation to the anion is investigated.     

Monte Carlo simulations of Na atoms in dynamically disordered Ar systems: Solid,liquid, and critical-point fluid Ar

We present the results of simulations of the structures and optical absorption spectra of Na atoms in solid and liquid Ar at its triple point, and in critical-point Ar fluid. The spectral simulations combine a classical Monte Carlo scheme for generating thermally accessible ground state configurations, along with a first-order perturbation theory treatment of the interactions between the excited Na^*(3p ²P) atom and the surrounding Ar perturbers [Boatz and Fajardo, J. Chem. Phys., 101 , 3472 (1994)]. These simulations predict a “triplet” (i.e., three peaks) absorption lineshape for Na atoms in solid and liquid Ar at its triple point, and an asymmetrical, blue degraded absorption band for Na atoms in critical Ar fluid. We also note and discuss the similarities between the simulated Na/Ar₍₁₎ lineshape and an experimental Li/Ar/Xe mixed host matrix spectrum, and the similarities between the simulated spectrum of Na atoms in critical point Ar fluid, and an experimental Li/H₂ matrix absorption spectrum. © 1997 by John Wiley & Sons, Inc.     

Hypergolic ionic liquids to mill, suspend, and ignite boron nanoparticles

Boron nanoparticles prepared by milling in the presence of a hypergolic energetic ionic liquid (EIL) are suspendable in the EIL and the EIL retains hypergolicity leading to the ignition of the boron. This approach allows for incorporation of a variety of nanoscale additives to improve EIL properties, such as energetic density and heat of combustion, while providing stability and safe handling of the nanomaterials.     

Synthesis and Characterization of Fluorodinitroamine,FN(NO2)2

NF₃ and N(NO₂)₃ are known compounds, whereas the mixed fluoronitroamines, FN(NO₂)₂ and F₂NNO₂, have been unknown thus far. One of these, FN(NO₂)₂, has now been prepared and characterized by multinuclear NMR and Raman spectroscopy. FN(NO₂)₂ is the first known example of an inorganic fluoronitroamine. It is a thermally unstable, highly energetic material formed by the fluorination of the dinitramide anion using NF₄⁺ salts as the preferred fluorinating agent.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.     

Condensation reaction of C4H4 with pyridine

C₄H₄⁺ reacts with pyridine (C₅H₅N) via the channels of proton transfer, charge transfer and condensation with H-elimination. The condensation reaction is of general interest in terms of basic chemistry and is the focus of the present study. By means of theoretical calculations and Fourier transform mass spectrometer experiments using deuterated pyridine and substituted pyridines, the structure of the product ion and the reaction pathways are investigated. From the experimental results we find that the H atom that is eliminated can originate from either pyridine or C₄H₄⁺. The experiments show that elimination of an H atom from C₄H₄⁺ is preferred and that there is an observable kinetic isotope effect. By replacing H atoms with methyl groups in ortho positions of pyridine, the experimental results also suggest possible steric blocking to the condensation. Based on the experimental observations and results of theoretical calculations of several possible structures of intermediates, transition states, and final product ions, a possible reaction scheme for the condensation-H-elimination is discussed.