An Erratum to this paper has been published: https://doi.org/10.1134/S199079312435001X

На основе расчетных значений энтальпий образования ряда гипотетических трис(пирроло)-, трис(диазоло)бензолов и 1,3,5-азинов в газовой фазе оценены величины энтальпий образования этих соединений в конденсированной фазе. Проведен анализ их эффективности как компонентов (основных энергетических компонентов или пластификаторов связующего) смесевых модельных твердых ракетных топлив или как энергетических компонентов неметаллизированных твердых топлив (ТТ) для газогенераторных двигателей (ГГД). Установлено, что полинитропроизводные предложенных пиррол-, пиразол- и имидазолсодержащих тетрациклов могут найти применение в качестве пластификаторов активного связующего в составах смесевых ракетных топлив, в том числе на основе гидрида алюминия (ГА), металлического алюминия и в составах без металла, обеспечивающих более высокую баллистическую эффективность на всех трех ступенях ракетных систем (РС) по сравнению с аналогичными топливными композициями с использованием наиболее перспективных современных пластификаторов, например динитрофуразана (ДНФ), нитроглицерина (НГЦ) или тетранитрометана (ТНМ). Расчетами показано, что изученные тетрациклы, не содержащие нитрогрупп, могут служить в качестве высокоэнтальпийных компонентов (ВЭК) в топливных рецептурах для ГГД, обеспечивающих более высокую баллистическую эффективность относительно бинарной рецептуры диспергатора с каучуком.

The paper presents the study of the calculated physicochemical properties of new high-energy 5/6/5 tricyclic structures, which are 1,2,3,4- or 1,2,4,5-tetrazines, fused with a pair of 1H-1,2,4-, 4H-1,2,4- or 1H-1,2,3-triazoles. Values of the enthalpy of formation in the gaseous phase have been determined by high-performance quantum-chemical calculations (within Gaussian 09 program package) using various methods for solving the stationary Schrödinger equation, including G4, G4MP2, ωB97XD/aug-cc-pVTZ, CBS-APNO, CBS-QB3, CBS-4M, B3LYP/6-311+G(2d,p), M062X/6-311+G(2d,p). The results of calculations obtained by the methods of atomization and isogyric reactions have been analysed. Various calculation methods have been compared in terms of accuracy and time consumption.

To identify promising areas for the search for high-energy materials (HEMs), there is an urgent need for a comprehensive analysis of the energy potential of compounds of various classes. This paper studies the energy potential of some organic compounds containing the –N=N(O)–C(NO2)3 fragment in their structure as plasticizers of a polymeric binder in solid composite propellants. Nine trinitromethyl-ONN-azoxy-derivatives of furazan and one similar methane compound are studied, four of which are actually synthesized substances, the rest are still hypothetical structures. The ballistic efficiency of solid composite propellants of three different types (without metal, with aluminum, and with aluminum hydride (AH)) in which one of the studied compounds with a trinitromethyl-ONN-azoxy fragment acts as a plasticizer of the polymer binder is assessed. The values of its enthalpy of formation and density are determined by calculation. A comparative analysis of the ballistic efficiency of such propellants with similar compositions containing the most powerful of the currently considered energy-intensive components (nitroglycerin, tetranitromethane, or dinitrofurazan) as a plasticizer shows that practically all the studied representatives of the class of trinitromethyl-ONN-diazene oxides are significantly superior in terms of ballistic efficiency to the reference plasticizers.

The relativistic pseudo-Jahn-Teller effect 2T x (t2 + e) = (E1/2 + G3/2) x (t2 + e) and the Jahn-Teller effect 2E x (t2 + e) = G3/2 x (t2 + e) are considered, employing the microscopic (Breit-Pauli) spin-orbit coupling operator. The orbital and spin-orbital parts of electronic Hamiltonian are expanded up to the second order terms in normal modes. Five-dimensional (t2 +e) potential energy surfaces are obtained in analytical form as functions of in-variants of the Td group.

The paper presents a study of the thermochemical properties of a series of substances containing an azoxy group associated with a trinitromethyl group and a furazan ring and promising for the creation of new high-energy density materials. The enthalpies of formation in the gaseous phase have been obtained by quantum chemical calculations using the Gaussian program package (G4MP2 and G4 methods). We compare the methods of atomization and of homodesmotic reactions in terms of accuracy, efficiency, and computational requirements. Also, we suggest an extension of the method of homodesmotic reactions which makes it possible to reduce the requirements for computing resources. We analyze the dependence of the enthalpy of formation on the structure of the compounds.

The paper presents the results of quantum-chemical calculations of physicochemical properties (structures, IR spectra, enthalpies of formation) of some 5/6/5 tricyclic systems: 1,2,3,4and 1,2,4,5-tetrazines annelated with trinitropyrroles and dinitropyrazoles (general formula C(6)N(10)O(8 )and C8N10O12). Calculation methods of various levels (G4, G4MP2, omega B97XD/aug-cc-pVTZ, CBS-QB3, CBS-4 M, B3LYP/6-311 + G(2d,p), M062X/6-311 + G(2d, p)) have been used and comparatively assessed, as well as different methods for calculating the enthalpy of formation. The calculation results obtained at the omega B97XD/aug-cc-pVTZ level differ by 0.3-7% (3-54 kJ/mol) from those obtained at the G4MP2 level, but the former method takes 4-8 times less time to calculate than the latter one.

This analysis is based on taking into account the spin–orbit interaction in the form of the Breit–Pauli operator in the electron Hamiltonian of the molecule. As the latter, we consider the Hamiltonian of the octahedral molecule Ỹ X_6 with an odd number of electrons and a heavy central atom Ỹ in the orbital 2D state with one outer electron and six X-ligand atoms forming a closed electron shell. The key element of the analysis is the construction of symmetrized combinations of products of eg modes and Pauli matrices, followed by the expansion of the electron Hamiltonian in a Taylor series in terms of the mentioned symmetrized combinations. In this case, the contributions of the main, first, and second orders in terms of powers according to the eg mode of normal vibrations are taken into account. A 6 × 6 vibronic matrix dependent on two eg modes is calculated in the diabatic electron basis constructed from the products of the components of the orbital D states and electronic spin functions. The vibronic matrix includes four electrostatic parameters and four parameters of spin–orbit origin. The eigenvalues of the vibronic matrix (i.e., potential energy surface) are invariant under the operations of the molecular symmetry group O_h^'.

A two-electron model that describes the singlet-triplet interaction of the 1Σ+ and 3Π states in linear triatomic molecules is proposed in this study. The analysis is based on the consideration of the spin-orbital coupling in an electronic Hamiltonian and the use of its symmetry properties. It is shown that the symmetry operators of the electronic Hamiltonian include both spatial (which affect the electronic coordinates) and matrix (which affect the electronic spins) operations. This study takes into account only the deformation π modes, and the resulting 7 × 7 vibronic matrix in fact describes the relativistic pseudo-Renner effect (3Π + 1Σ+) × π. The eigenvalues of the vibronic matrix (i.e., potential energy surfaces) have axial symmetry. The vibronic matrix includes nine parameters. Three of them have an electrostatic origin, and six parameters are determined by the spin-orbital coupling.

DFT calculations at the B3LYP/6-311+G(2d,p) level and combined G4(MP2) and G4 methods within the GAUSSIAN-09 software package have been used to evaluate the standard enthalpies of formation of species in the gas phase (kJ/kg): C4N8O6 (2854.0), C4HN7O4 (2932.3), C4H2N6O2 (3104.8), C2N6O4 (4252.6), C2N8O4 (4395.9), C2N6O3 (4645.6), C2N8O4 (4755.2), C2HN7O2 (4815.7), C4N6O2 (5153.2), and C4N8O2 (5609.1). For experimentally studied compounds C2N6O4, C2N6O3, and C2N8O4, the $${{\Delta }_{f}}H_{{298}}^{^\circ }\left( {\text{g}} \right)$$ values calculated at the G4 level are 8–15% larger than the experimental values, which is almost half as large as the scatter of the experimental values for these compounds. The thermochemical data, IR absorption spectra, structural parameters, and atomic displacements for the strongest vibrations of high-energy compounds C4N8O6, C4HN7O4, C4H2N6O2, C2N8O4, C2HN7O2, C4N6O2, and C4N8O2 have been determined for the first time. It has been demonstrated that, for the compounds studied, the G4(MP2) and G4 computation levels give very close values (within 1–3%), which leads to significant saving in computational time (three- to eightfold). However, B3LYP/6-311+G(2d,p) calculations give values differing by 2–11% from the G4 values. The obtained data can be used as a reference and make it possible to distinguish the most promising groups of substances for operation as high-energy components of promising fuel.

•We obtained all elements of symmetry group (spin-orbital interaction is accounted).•Vibronic symmetry operators and time reversal operator are constructed.•Vibronic matrix 4 × 4 of relativistic pseudo effect of Renner is deduced.•Potential energy surfaces are analyzed.

The paper introduces the 4x4 vibronic matrix that describes singlet-triplet interaction of adiabatic terms (1)Sigma(+) and (3)Sigma(+) via deformation z-modes of the linear triatomic system. Our analysis takes into account spin-orbital coupling in ab initio Breit-Pauli form in the framework of two-electronic model. It is shown that the symmetry operators of electronic Hamiltonian include both space operations (acting on electronic coordinates) and matrix operations (acting on electronic spins). Eigenvalues of vibronic matrix (i.e. potential energy surfaces) are invariants of the molecular symmetry group C-infinity nu. The 4x4 vibronic matrix includes 4 electrostatic parameters and 3 parameters caused by spin-orbital interaction.

The energetic capabilities of three energy-intensive components containing furoxan cycles and azo groups are studied. These compounds are assessed as the main fillers of composite solid rocket fuels. It is shown that the energy efficiency of the considered compounds increases in the following order: 3,3'‑di(4-nitrofuroxan-3-yl)-5,5'-azo-1,2,4-oxadiazole (I) < (Z)-tris ([1,2,5]oxadiazolo)[3,4-c:3',4'-e:3'',4''-g][1,2]diazocine 1,4,11-trioxide (III) < 4,4'-dinitro-3,3'-azofuroxan (II).

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Currently, new approaches are being actively developed to obtain promising new generation rocket fuels that meet the strict requirements set on the energy content of their components. One such approach is a computer design of new substances, as a rule, not yet synthesized but promising for the creation of components of new fuels. The thermochemical properties of a number of substances structurally similar to 1,4‑diethynylbenzene (DEB) С10Н6 (C18H8, C26H10, С19H10, and C16H8) are studied in this paper. The thermochemical properties are calculated quantum-chemically with the Gaussian 09 software, which makes it possible to accurately obtain the enthalpies of the formation of the studied substances. The G4 combined method included in Gaussian 09 is used as the main one to calculate the enthalpies of the formation of molecules.

In recent decades, the chemistry of rocket propellants has been actively developing in the direction of searching for new high enthalpy polynitrogen compounds, since their use can provide higher energy characteristics of propellants, explosive compositions, and explosives than the use of traditional low enthalpy oxidizers with high oxygen content, for example, ammonium perchlorate. The level of energy characteristics that can be provided when using these energy-intensive compounds should be supposed before starting the search for methods to synthesize these compounds. Since the enthalpy of formation is one of the main parameters that determine the energy potential of a component, many methods have been developed for the theoretical estimation of the enthalpy of formation. The paper presents a study of the regularities of the dependence of the enthalpy of formation of nine conjugated N-heterocycle compounds on their structure and exhibits the principles of creating solid composite propellants with maximum ballistic efficiency based on each of the compounds studied. Calculations of the enthalpies of formation in the gas phase of the substances under study were performed using the Gaussian 09 program.