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The development of high-performance catalysts for eliminating the negative effects of hazardous contaminants is highly desirable. In this study, a nanogold-immobilized catalyst based on hydroxyapatite nanowire (HN)-sintered porous ceramic beads with excellent catalytic performance in the reductive degradation of nitrobenzene compounds has been prepared. The high-aspect-ratio HN self-assembles into a network structure and acts as a building block for forming the porous ceramic beads with an interconnected porous architecture and high porosity features. The ceramic skeleton with enriched anchoring sites can offer enough traction to disperse the stable gold nanoparticles (AuNPs) during the catalytic reaction process. The prepared HN/AuNP beads are analyzed by several characterization methods and demonstrate unique properties, such as micron-sized and interconnected porous channels, adjustable porosity, and good distribution of AuNPs. In addition, the HN/AuNP beads exhibit high catalytic activity in the reductive degradation of 4-nitrophenol by sodium borohydride. The HN/AuNP beads can be recycled, retaining their original conversion efficiency at about 97% even after 15 consecutive reaction cycles. Besides, the HN/AuNP beads maintain high catalytic stabilities after several high-temperature heat treatment procedures. Furthermore, the highly effective catalytic reduction conversion of several nitrobenzene compounds into the corresponding amino derivatives is achieved. The developed porous ceramic beads can be used for supporting various nanocatalysts. These results demonstrate that the catalytic porous beads are promising for applications in water treatment and high-temperature catalysis fields.

Three adducts SF4·BF3, SF4·AsF5, and SF4·SbF5 were studied in this work, in gas phase, DFT method was performed to study their molecular structures and thermodynamic properties. The heat of formati...

The molecular and crystal structure of the adduct NF3⋅BF3 was studied computationally using density functional theory. It shows that the adduct exists in the form of a complex but is not ionic. The heats of formation in the gas and the condensed phase of the adduct are −1266.09 and −1276.37 kJ ⋅mol−1, respectively, which indicates that it is stable under atmospheric conditions. The crystal form belongs to P21/c space group. The calculated large band gap (ΔE g) of the crystal proves that it is stable. The conduction band (LUCO) is mainly contributed by the p orbital of N atom and the valence band (HOCO) from the p orbital of F atom.

The molecular geometries and electronic structures of 14 fluorides are optimized using density functional theory (DFT) B3LYP/6-31G*, B3P86/6-31G* and Moller–Plesset perturbation theory MP2/6-31G* methods. EHOMO, ELUMO, ΔE, μ, QF, QM and V are chosen as the structural descriptors. The acute toxicity (−lg LC50) of fluorides to rats along with the above structural parameters are used to establish the quantitative structure–activity relationships (QSARs). The results show that the models based on the DFT-B3LYP/6-31G* is better than that based on B3P86/6-31G* and MP2/6-31G* methods. The toxic mechanism is controlled mainly by electronic factor QF (the maximum net atomic charge on fluorides). The QSAR relationship between the electronic parameters QF and the toxicity −lg LC50 is: −lg LC50 = 0.032 + 7.037QF ( R adj 2 = 0.869 , SE = 0.37097, F = 27.578, P = 0.013). An overall cross-validation correlation coefficient is then obtained using leave-one-out method and the calculated cross-validation coefficient (q2) value is 0.660. The predicted toxic values using the above equation are in good agreement with the experimental values, and the QSAR model has good stability and strong prediction ability.

The intramolecular hydrogen-bonding interactions and properties of a series of nitroamino[1,3,5]triazine-based guanidinium salts were studied by using the dispersion-corrected density functional theory method (DFT-D). Results show that there are evident LP(N or O; LP = lone pair)→σ*(N-H) orbital interactions related to O⋅⋅⋅H-N or N⋅⋅⋅H-N hydrogen bonds. Quantum theory of atoms in molecules (QTAIM) was applied to characterize the intramolecular hydrogen bonds. For the guanidinium salts studied, the intramolecular hydrogen bonds are associated with a seven- or eight-membered pseudo-ring. The guanylurea cation is more helpful for improving the thermal stabilities of the ionic salts than other guanidinium cations. The contributions of different substituents on the triazine ring to the thermal stability increase in the order of -NO(2)

Periodic density functional theory calculations are performed to study the hydrostatic compression effects on the structure, electronic, and thermodynamic properties of the energetic polyazide 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT) in the range of 0-100 GPa. At the ambient pressure, the local density approximation/Ceperley-Alder exchange-correlation potential parameterized by Perdew and Zunger relaxed crystal structure compares well with the experimental results. The predicted heat of sublimation is 38.68 kcal/mol, and the evaluated condensed phase of formation (414.04 kcal/mol) approximates to the experimental value. The detonation velocity and detonation pressure for the solid TAHT are calculated to be 7.44 km/s and 23.71 GPa, respectively. When the pressure is exerted less than 35 GPa, the crystal structure and geometric parameters change slightly. However, at 36 GPa, the molecular structure, band structure, and density of states change abnormally because of the azide-tetrazole transformation that has not been observed in gas phase or polar solvents. The azido group cyclizes to form a five-membered tetrazole ring that is coplanar with the riazine ring and contributes to a larger conjunction system. As the pressure augments further to 80 GPa, the hydrogen transfer is found and a new covalent bond H2-N9 is formed. In the studied pressure range, the band gap decreases generally except for some breaks due to the molecular transformation and drops to nearly zero at 100 GPa, which means the electronic character of the crystal changes toward a metallic system. An analysis of the electronic structure shows that an applied pressure increases the impact sensitivity of TAHT.

A detailed study on the structural, electronic, and thermodynamic properties of the solid polyazide 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine (TAAT) under the hydrostatic pressure of 0–100 GPa was performed using the plane-wave density function theory method. The predicted crystal structure compares well with the experimental results at the ambient pressure. The results show that a pressure less than 40 GPa does not significantly change the crystal and molecular structures. When the higher pressure is applied, the molecular geometry, band structure, and density of states change regularly except at 48 and 90 GPa where the azide–tetrazole transformation occurs. At 48 GPa, the tetrazole rings are almost coplanar with the triazine rings, whereas it has a big deviation at 90 GPa. The azide cyclization for polyazido-1,3,5-triazine has not been observed in the gas phase or polar solvents. Moreover, the band gap reduction is more pronounced in the low-pressure range than in the high-pressure region. The band gap d...

Density function theory has been employed to study a series of compounds containing pyridine ring at the B3LYP/6-31G* level. Detonation performance was evaluated by using the Kamlet–Jacobs equations based on the calculated densities and heats of formation. Some compounds have high densities (ca. 1.9 g cm−3) and good performance (detonation velocities over 9 km s−1, detonation pressures about 39 GPa) and may be the potential candidates of high energy density materials. The thermal stability and the pyrolysis mechanism of the title compounds were investigated by the bond dissociation energies and the impact sensitivity predicted. Solvent effect has been investigated and it makes the title compounds more stable in solutions.

A new polynitro cage compound 2, 4, 6, 8, 10, 12, 13, 14, 15-nonanitro-2, 4, 6, 8, 10, 12, 13, 14, 15-nonaazaheptcyclo [5.5.1.1(3,11).1(5,9)] pentadecane (NNNAHP) was designed in the present work. Its molecular structure was optimized at the B3LYP/6-31 G(d,p) level of density functional theory (DFT) and crystal structure was predicted using the Compass and Dreiding force fields and refined by DFT GGA-RPBE method. The obtained crystal structure of NNNAHP belongs to the P-1 space group and the lattice parameters are a = 9.99 Å, b = 10.78 Å, c = 9.99 Å, α = 90.01°, β = 120.01°, γ = 90.00°, and Z = 2, respectively. Based on the optimized crystal structure, the band gap, density of state, thermodynamic properties, infrared spectrum, strain energy, detonation characteristics, and thermal stability were predicted. Calculation results show that NNNAHP has detonation properties close to those of CL-20 and is a high energy density compound with moderate stability.

Ab initio calculations have been performed using the complete basis set model (CBS-QB3) to study the reaction mechanism of butane radical (C(4)H(9)•) with oxygen (O(2)). On the calculated potential energy surface, the addition of O(2) to C(4)H(9)• forms three intermediates barrierlessly, which can undergo subsequent isomerization or decomposition reaction leading to various products: HOO• + C(4)H(8), C(2)H(5)• + CH(2)CHOOH, OH• + C(3)H(7)CHO, OH• + cycle-C(4)H(8)O, CH(3)• + CH(3)CHCHOOH, CH(2)OOH• + C(3)H(6). Five pathways are supposed in this study. After taking into account the reaction barrier and enthalpy, the most possible reaction pathway is C(4)H(9)• + O(2) → IM1 → TS5 → IM3 → TS6 → IM4 → TS7 → OH• + cycle-C(4)H(8)O.

A series of azidamines were studied at the B3LYP/6-311+G(2df) level of density functional theory. Thermodynamic properties were calculated and increased quantitatively with the increasing temperature as well as the number of azido groups. The azidamines are highly energetic with large enthalpies of formation. The detonation performances of the azidamines were evaluated and their performances are comparable to those of hexahydro-1,3,5-trinitro-1,3,5-trizine and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane. However, they are sensitive to impact as well as halogen azides according to the small potential energy barriers.

The heats of formation of ClF, ClF 3 , ClF 5 , ClFO, ClFO 2 , ClFO 3 , ClF 3 O 2 , ClF 3 O, and ClF 5 O have been calculated with the help of atomization reaction (AR), formation reaction (FR), and modified formation reaction (MFR) at the G3 and G3X (X = B3, MP2, and MP2B3) levels. FR or MFR in conjunction with the G3 theory can give accurate results close to experimental values. The standard thermodynamic functions of the title compounds have also been evaluated and the results agree well with the available experimental data. Results show that ClF, ClF 3 , ClF 5 and ClF 3 O are stable at the room temperature, and ClFO 2 , ClF 3 O 2 , and ClF 5 O may be stable at lower temperature.

In an attempt to find superior propellants, 2-diazo-4,6-dinitrophenol (DDNP) and its -NO(2), -NH(2), -CN, -NC, -ONO(2), and -NF(2) derivatives were studied at the B3LYP/6-311++G level of density functional theory (DFT). Sensitivity was evaluated using bond dissociation enthalpies (BDEs) and molecular surface electrostatic potentials. The C-NO(2) bond appears to be the trigger bond during the thermolysis process for these compounds, except for the -ONO(2) and -NF(2) derivatives. Electrostatic potential results show that electron-withdrawing substituents make the charge imbalance more anomalous, which may change the strength of the bond, especially the weakest trigger bond. Most of the DDNP derivatives have the impact sensitivities that are higher than that of DDNP, making them favorable for use as solid propellants in micro-rockets. The theoretical densities (ρ), heats of formation (HOFs), detonation energies (Q), detonation pressures (P), and detonation velocities (D) of the compounds were estimated. The effects of various substituent groups on ρ, HOF, Q, D, and P were investigated. Some derivatives exhibit perfect detonation properties. The calculated relative specific impulses (I (r,sp)) of all compounds except for -NH(2) derivatives were higher than that of DDNP, and also meet the requirements of propellants.

Polynitro cage compound 4-trinitroethyl-2,6,8,10,12-pentanitrohexaazaisowurtzitane has the same framework with but higher stability than CL-20 and is a potential new high energy density compound (HEDC). In this paper, the B3LYP/6-31G(d,p) method of density functional theory (DFT) has been used to study its heat of formation, IR spectrum, and thermodynamic properties. The stability of the compound was evaluated by the bond dissociation energies. The calculated results show that the first step of pyrolysis is the rupture of the N-NO(2) bond in the side chain and verify the experimental observation that the title compound has better stability than CL-20. The crystal structure obtained by molecular mechanics belongs to the P2(1)2(1)2(1) space group, with lattice parameters a = 12.59 Å, b = 10.52 Å, c = 12.89 Å, Z = 4, and ρ = 2.165 g·cm(-3). Both the detonation velocity of 9.767 km·s(-1) and the detonation pressure of 45.191 GPa estimated using the Kamlet-Jacobs equation are better than those of CL-20. Considering that this cage compound has a better detonation performance and stability than CL-20, it may be a superior HEDC.

Density functional theory (DFT) methods have been applied to study the properties of series of N5 + salts. The thermal stabilities of the crystals are evaluated based on the reaction enthalpy (ΔH) and free energy change (∆G) of the salts when they dissociate into neutral products. The energy outputs of salts in explosion indicate that all N5 + salts yield large energy except for N5SbF6 and N5Sb2F11. Considering the released energy and thermal stability, (N5)2SnF6, N5PF6, N5BF4, and N5SO3F may be potential candidates of very energetic explosives.

Ninety-one nitro and hydroxyl derivatives of benzene were studied at the B3LYP/6-31G∗ level of density functional theory. Detonation properties were calculated using the Kamlet-Jacobs equation. Three candidates (pentanitrophenol, pentanitrobenzene, and hexanitrobenzene) were recommended as potential high energy density compounds for their perfect detonation performances and reasonable stability. The pyrolysis mechanism was studied by analyzing the bond dissociation energy (BDE) and the activation energy (Ea) of hydrogen transfer (H–T) reaction for those with adjacent nitro and hydroxyl groups. The results show that Ea is much lower than BDEs of all bonds, so when there are adjacent nitro and hydroxyl groups in a molecule, the stability of the compound will decrease and the pyrolysis will be initiated by the H–T process. Otherwise, the pyrolysis will start from the breaking of the weakest C–NO2 bond, and only under such condition, the Mulliken population or BDE of the C–NO2 bond can be used to assess the relative stability of the compound.

The density functional theory has been used to study the tautomeric equilibrium of 2-diazo-4,6-dinitrophenol(DDNP) in the gas phase and in 14 solvents at the B3LYP/6-31G* level. The solvent effects on the tautomeric equilibria were investigated by the self-consistent reaction field theory (SCRF) based on conductor polarized continuum model (CPCM) in apolar and polar solvents and by the hybrid continuum-discrete model in protic solvent, respectively. Solvent effects on the computed molecular properties, such as molecular geometries, dipole moments, ELUMO, EHOMO, total energies for DDNP tautomers and transition state, tautomerization energies and solvation energies have been found to be evident. The tautomeric equilibrium of DDNP is solvent-dependent to a certain extent. The tautomer I (cyclic azoxy form) is preferred in the gas phase, while in nonpolar solvents tautomer I and II (quinold form) exist in comparable amounts, and in highly polar solvents, the tautomeric equilibrium is shifted in favor of the more polar tautomer II. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Thirty nitro aromatic compounds are studied using the density functional theory B3LYP method with six basis sets (3-21G, 6-31G, 6-31G∗, 6-31G∗∗, 6-311G∗ and 6-31+G∗∗) and semiempirical PM3 method. Based on the geometries optimized at various theoretical levels, the molecular volumes and densities are calculated. Compared with the experimental results, the densities estimated by the PM3 and B3LYP/3-21G methods are all systematically larger, and that obtained with the other five basis sets are better and quite accurate. Considering that a larger basis set demands more computer resource, B3LYP/6-31G or 6-31G∗ is recommended for rapid and reliable prediction of crystalline densities. The effect of various groups on the densities is discussed. Based on the theoretical densities, it is possible to estimate the detonation properties, which will be helpful to rapidly and effectively design and screen promising candidates of high energy density materials (HEDMs).

The nitro derivatives of toluenes are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. Detonation properties are evaluated using the modified Kamlet–Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure and the number of nitro and methyl groups. Thermal stability and the pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies at the unrestricted B3LYP/6-31G* level. The activation energies of H-transfer reaction are smaller than the BDEs of all bonds and this illustrates that the pyrolysis of the title compounds may be started from the isomerization reaction of H transfer. According to the quantitative standard of energetics and stability as an HEDC (high energy density compound), pentanitrotoluene essentially satisfies this requirement. In addition, we have discussed the effect of the nitro and methyl groups on the static electronic structural parameters and the kinetic parameter.

Density functional theory calculations were performed to find comprehensive relationships between the structures and performance of a series of highly energetic cyclic nitramines. The isodesmic reaction method was employed to estimate the heat of formation. The detonation properties were evaluated by using the Kamlet-Jacobs equations based on the theoretical densities and HOFs. Results indicate the N-NO(2) group and aza N atom are effective substituents for enhancing the detonation performance. All cyclic nitramines except C11 and C21 exhibit better detonation performance than HMX. The decomposition mechanism and thermal stability of these cyclic nitramines were analyzed via the bond dissociation energies. For most of these nitramines, the homolysis of N-NO(2) is the initial step in the thermolysis, and the species with the bridged N-N bond are more sensitive than others. Considering the detonation performance and thermal stability, twelve derivatives may be the promising candidates of high energy density materials (HEDMs). The results of this study may provide basic information for the further study of this kind of compounds and molecular design of novel HEDMs.

Studies have suggested that octanitrocubane (ONC) is one of the most powerful non-nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro-1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm(3), and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P2(1)2(1)2(1), and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM.

In this work, the properties of the synthesized high-nitrogen compounds 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT) and 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT), and a set of designed bridged triazines with similar bridges were studied theoretically to facilitate further developments for the molecules of interests. The gas-phase heats of formation were predicted based on the isodesmic reactions by using the DFT-B3LYP/AUG-cc-PVDZ method. The estimates of the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. Calculation results show that the method gives a good estimation for enthalpies, in comparison with available experimental data for TAAT and TAHT. The crystal density has been computed using molecular packing calculations. The calculated detonation velocities and detonation pressures indicate that -NF(2), -NO(2), -N═N-, and -N═N(O)- groups are effective structural units for improving the detonation performance of the bridged triazines. The synthesized TAAT and TAHT are not preferred energetic materials due to their inferior detonation performance. The p→π conjugation effect between the triazine rings and bridges makes the molecule stable as a whole. The electrostatic behavior of the bridged triazines is characterized by an anomalous surface potential imbalance when incorporating the strongly electron-withdrawing -NF(2) and -NO(2) groups into the molecule. An analysis of the bond dissociation energies shows that all these derivatives have good thermal stability over RDX and HMX, and the -NH-NH- bridge is more helpful for improving the stability than -N═N(O)- and -N═N- bridges. Considering the detonation performance and thermal stability, three bridged triazines may be considered as the potential candidates of high-energy density materials (HEDMs).

Two new nitramine compounds containing pyridine, 1,3,5,7-tetranitro-8-(nitromethyl) -4-imidazolino[4,5-b]4-imidazolino-[4,5-e]pyridine and its N-oxide 1,3,5,7-tetranitro-8- (nitromethyl)-4-imidazolino[4,5-b]4-imidazolino-[4,5-e]pyridine-4-ol were proposed. Density functional theory (DFT) has been employed to study the molecular geometries, electronic structures, infrared spectra, and thermodynamic properties at the B3LYP/6-31G* level. Their detonation performances evaluated using the Kamlet-Jacobs equations with the calculated densities and heats of formation are superior to those of HMX. The predicted densities of them were ca. 2 g cm(-3), detonation velocities were over 9 km s(-1), and detonation pressures were about 40 GPa, showing that they may be potential candidates of high energy density materials (HEDMs). The natural bond orbital analysis indicated that N-NO(2) bond is the trigger bond during thermolysis process. The stability of the title compounds is slightly lower than that of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane (CL-20). The results of this study may provide basic information for the molecular design of new HEDMs.

A new polynitro cage compound with the framework of HNIW and a tetrazole unit, i.e., 10-(1-nitro-1, 2, 3, 4-tetraazol-5-yl)) methyl-2, 4, 6, 8, 12-hexanitrohexaazaisowurtzitane (NTz-HNIW) has been proposed and studied by density functional theory (DFT) and molecular mechanics methods. Properties such as IR spectrum, heat of formation, thermodynamic properties, and crystal structure were predicted. The compound belongs to the Pbca space group, with the lattice parameters a = 15.07 Å, b = 12.56 Å, c = 18.34 Å, Z = 8, and ρ = 1.990 g·cm(-3). The stability of the compound was evaluated by the bond dissociation energies and results showed that the first step of pyrolysis is the rupture of the N-NO(2) bond in the side chain. The detonation properties were estimated by the Kamlet-Jacobs equations based on the calculated crystal density and heat of formation, and the results were 9.240 km·s(-1) for detonation velocity and 40.136 GPa for detonation pressure. The designed compound has high thermal stability and good detonation properties and is probably a promising high energy density compound (HEDC).

Aliphatic polynitrates are studied using the density functional theory B3LYP method with basis set 6-31G*. The assigned infrared spectrum is obtained and is used to compute the thermodynamic properties based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics. On comparison of the theoretical densities with the experimental ones, the reliability of this theoretical method is tested. Detonation properties are evaluated using the modified Kamlet-Jacobs equations based on the calculated densities and heats of formation. According to the largest exothermic principle, the relative specific impulse (Is) is investigated by calculating the enthalpy of combustion (ΔH comb ) and the total heat capacity (C p,gases ). It is found that the introduction of methylene nitrate group could decrease the specific impulses on whole. Moreover, in combination with the energetic properties, xylitol pentanitrate, mannitol hexanitrate, volemitol heptanitrate, and 1,2,3,4,5,6,7,8-octanitrate n-octane are potential candidates for high energy density compounds.

The derivatives of DPO (2,5-dipicryl-1,3,4-oxadiazole) are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. The bond length is focused to primarily predict thermal stability and the pyrolysis mechanism of the title compounds. Detonation properties are evaluated using the modified Kamlet-Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure, and the number of azido, nitrate, and nitramine groups. According to the largest exothermic principle, the relative specific impulse is investigated by calculating the enthalpy of combustion (ΔH(comb)) and the total heat capacity (C(p,gases)). It is found that the introduction of -N(3), -ONO(2), and -NNO(2) groups could increase the specific impulses and II-4, II-5, and III-5 are potential candidates for High Energy Density Materials (HEDMs). The effect of the azido, nitrate, and nitramine groups on the structure and the properties is discussed.