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Context: Based on the methods of quantum chemistry and atom–atom potentials, the molecular and crystal structure of a number of high-energy pyrazines was modeled: unsubstituted diazines, as well as fully nitrated 1,4-diazabenzenes, their oxides and polymorphs. The enthalpies of formation, densities of molecular crystals, and some performance characteristics of these compounds were determined. The parameters of decomposition of substances were estimated. It has been established that tetranitropyrazine-1,4-dioxide has maximum energy content and excellent performance characteristics, which determine the prospects for using this compound as a high-energy one in the considered series of compounds. Methods: In this work, DFT calculations were conducted through the software Gaussian 09 using B3LYP functional with basis set aug-cc-PVDZ and the Grimme dispersion correction D2. For crystal structure optimization, the atom–atom potential methods with PMC program (Packing of Molecules in Crystal) were used. Charges for molecular electrostatic potential were fitted by FitMEP and enthalpies of formation in gas phase were assessed by G3B3. [ABSTRACT FROM AUTHOR]

The crystal structure of substituted formamidine salts has been modeled on the basis of a combination of quantum chemistry methods and atom–atom potentials. Based on the new author's method (MICCM) for calculating the enthalpies of formation of salts, which is based on the model of a cocrystal consisting of a mixture of cations and anions and a "quasi-salt" of the neutral components of the salt itself, the formation enthalpy is calculated as the average between the enthalpies of formation of these two structural components for salts various formamidines and the contributions of the corresponding cations to the calculation scheme are given. The results are in good agreement with the experimental data obtained by combustion calorimetry. [ABSTRACT FROM AUTHOR]

Simulation of crystal structures of series 1(2)‐R‐1(2)H‐[1,2,3]triazolo[4,5‐e][1,2,3,4]tetrazine 5,7‐dioxides, 1,5,7‐trioxides, 4,6‐dioxides and 3,4,6‐trioxides was carried out using an original technique based on the method of atom‐atom potentials and quantum chemistry. The effect of the position of the substituent in the triazole ring on the change in the crystal structures of these compounds and their thermochemical characteristics was studied for the first time. For some of synthesized compounds, thermochemical characteristics were investigated and differential scanning calorimetry curves were obtained. Detonation parameters were calculated, on the basis of which the prospects for the use of the considered compounds were assessed. [ABSTRACT FROM AUTHOR]

Bifurazano[3,4‐b:3′,4′‐f][3′′,4′′‐d]xacycloheptatriene (BFFO, C6N6O5) is perspective high‐energy‐density compound. The crystal structure was previously determined for its monohydrate (space group P21/c, Z=4), while it remains unknown for pure BFFO being of primary interest. Herein a theoretical crystal structure prediction of BFFO in both monohydrated and the proposed anhydrous forms is performed. The Coulomb energy was calculated with advanced point charge models reproducing with high accuracy electrostatic potentials of the BFFO and water molecules. The van der Waals energy was calculated with empirical atom‐atom potentials. The global search for energy minima involved enumeration of 35 most likely organic structural classes with one and two independent molecules (Z=1 and 2). A characteristic feature of the energy landscape of an anhydrous BFFO is that the energies of the deepest minima differ very little. However the structures in the space group Pbca, Z=8 and P21/c, Z=8 were found the most energetically preferable. The common feature of predicted BFFO structures is the presence of herring‐bone packing motifs instead of stacking configurations. The detonation pressure and velocity of pure BFFO crystal (presumably a high‐energy explosive) are estimated from the predicted density; the latter occurs to be lower than density of the monohydrate form. [ABSTRACT FROM AUTHOR]

[Display omitted] Based on a combination of quantum chemistry and atom–atom potentials methods, we developed a technique for modeling the structure and estimating the complexation energy of a binary organic complex in gas and crystal phases. The efficiency of this technique was illustrated by an example of the benzotrifuroxan–benzene molecular complex. For both phases, the same molecular binary structure (π-stacking) was obtained with a parallel arrangement of the planes of BTF and benzene molecules and complexation energies of −11.9 and −11.7 kcal mol−1 for a gas phase and a crystal cluster, respectively. [ABSTRACT FROM AUTHOR]

X-ray study and computational modeling of [1,2,5]oxadiazole [3,4- e ][1,2,3,4]tetrazine 4,6-dioxide (FTDO)–benzene (1 : 1) solvate structure have been carried out. Using the Atom-Atom Potentials Method, the original methodology and elaborated program packings the crystal structure of pure FTDO was predicted. Image 1 • A global search for optimal packages of oxadiazolo tetrazine dioxide and its complex (1 : 1) with benzene were carried out. • The structure of complex was investigated by X-ray diffraction analysis. • Crystal structure prediction of pure oxadiazolo tetrazine dioxide was performed. [ABSTRACT FROM AUTHOR]