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Molecular dynamics simulations have been performed to investigate the effect of acetone solvent on the crystal morphology of RDX. The results show that the growth morphology of RDX crystal in vacuum is dominated by the (111), (020), (200), (002), and (210) faces using the BFDH laws, and (111) face is morphologically the most important. The analysis of surface structures of RDX crystal indicates that (020) face is non-polar, while (210), (111), (002), and (200) faces are polar among which (210) face has the strongest polarity. The interaction between acetone solvent and each RDX crystal face is different, and the order of binding energy on these surfaces is (210) > (111) > (002) > (200) > (020). The analysis of interactions among RDX and acetone molecules reveal that the system nonbond interactions are primary strong van der Waals and electrostatic interactions containing π-hole interactions, the weak hydrogen bond interactions are also existent. The effect of acetone on the growth of RDX crystal can be evaluated by comparing the binding energies of RDX crystalline faces. It can be predicted that compared to that in vacuum, in the process of RDX crystallization from acetone, the morphological importance of (210) face is increased more and (111) face is not the most important among RDX polar surfaces, while the non-polar (020) face probably disappears. The experimentally obtained RDX morphology grown from acetone is in agreement with the theoretical prediction. [ABSTRACT FROM AUTHOR]

The interaction of seven pamidronate bisphosphonate (Pami-BPs) and its analogs with the hydroxyapatite (HAP) (100) surface was studied using density functional theory (DFT) and molecular dynamic (MD) methods. Partial Mulliken oxygen atomic charges in protonated structures were calculated at the level of B3LYP/6-31G*. The MD simulation was performed using the Discover module of Material Studio by compass force field. The results indicate the abilities of donating electrons of the oxygen atoms of the phosphate groups that are closely associated with the antiresorptive potency. The binding energies, including vdw and electrostatic, are used to discuss the mechanism of antiresorption. The results of calculations show that the strength of interaction of the HAP (100) face with the bisphosphonates is N > N > N > N > N > N > N according to their experimental pIC values. [ABSTRACT FROM AUTHOR]

Density functional theory calculations using an SMD model were performed to investigate the effect of solvents (cyclohexanone, acetone, dimethyl formamide and dimethyl sulphoxide) on the crystal quality and sensitivity of RDX. The results indicate that the N-N bond length of the RDX molecule in solvents differs clearly from that in gas phase. The solvent effect on bond and dihedral angles of RDX molecule is small, however, the RDX molecule still maintains the AEE configuration. Natural population analysis shows that, due to solvation effects, RDX O atoms attract more electrons in solvents than in gas phase, while more positive charge distributes to the molecular skeleton. The calculations of N-NO bond BDE and nitro group charge as well as surface electrostatic potential parameters reveal that the solvent effect may be helpful to reduce the sensitivity of RDX, but this effect has an upper limit. Finally, it can be predicted qualitatively that the crystal quality of RDX crystallized from cyclohexanone and dimethyl sulphoxide will be higher than that from acetone and dimethyl formamide. Experimental results support these theoretical predictions. [ABSTRACT FROM AUTHOR]

Binary heterostructures Ag2ZrO3/TiO2 composites have been prepared by a facile calcination-hydrothermal, using ZrOCl2·8H2O, AgNO3, and TBOT as raw materials and PVP as a dispersant. X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectrometer, XPS, UV-vis DRS, and photoluminescence (PL) were employed to characterize the Ag2ZrO3/TiO2 composites. In an orthodox three-electrode system with RhB electrolyte solution, electrochemical measurements were carried out, and the results showed that it was a remarkable reversible reaction with reliable stabilization and favorable dynamics properties. The photocatalytic performances of Ag2ZrO3/TiO2 composites were estimated via the dilapidation of RhB under visible-light irradiation. In comparison to the pure TiO2, the photocatalytic presentation of Ag2ZrO3/TiO2 was enhanced. The presence of Ag2ZrO3 formed well-matched band level and constructed a heterogeneous interface to remarkably modify the bandgap energy with prolonged charge separation. The binary Ag2ZrO3/TiO2 composites can be regarded as a potential environmental material for applications in photocatalytic degradation of organic contaminants under visible-light irradiation. [ABSTRACT FROM AUTHOR]

The derivatives of 1,2,3,4-tetrazine may be promising candidates for high-energy density compounds and are receiving more and more attentions. In this study, a new derivative 6-amino-7-nitropyrazino[2,3-e][1,2,3,4]tetrazine 1,3,5-trioxide (ANPTTO) has been designed. The geometrical structure and IR spectrum in the gas phase were studied at the B3LYP/6-31G* level of density functional theory (DFT). The crystal structure was predicted by molecular mechanics method and refined by the GGA/BOP function of periodic DFT with the basis set of TNP. The gas phase enthalpy of formation was calculated by the homodesmotic reaction method. The enthalpy of sublimation and solid phase enthalpy of formation were also predicted. The detonation properties were estimated with the Kamlet-Jacobs equations based on the predicted density and enthalpy of formation in solid state. The available free space in the lattice and resonance energy were calculated to evaluate its stability. ANPTTO has a high stability and is a promising high energetic component with the density >2 g · cm, detonation velocity >9000 m · s, and detonation pressure >40 GPa. A synthetic route was proposed to provide a consideration for further study. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] The high energy density compound 3-azido-4-[(4-nitrofurazan-3-yl)- ONN-azoxy]furazan was synthesized from 3-amino-4-[(4-azidofurazan-3-yl)- NNO-azoxy]furazan by a catalytic oxidation process. The structure of the compound was characterized by IR, NMR spectroscopy and elemental analysis. The detonation performance of this compound was estimated by using density functional theory and the Monte Carlo method. The calculations predicted the density of the compound was 1.88 g·cm, the heat of detonation 1780.65 J·g, the detonation velocity 9150 m·s, and the detonation pressure 37.46 GPa. [ABSTRACT FROM AUTHOR]

To continue our previous work, the structure and some properties of a new series of 1,2,3,4-tetrazine 1,3-dioxides annulated with an imidazole ring or oxazole ring were studied in this paper. Four imidazolo-v-tetrazine 1,3-dioxides (ITDOs) I1-I4 and eight oxazolo-v-tetrazine 1,3-dioxides (OTDOs) O1-O8 were designed. We employed the density functional theory (DFT) in B3LYP/6-311++G(d,p) to study their geometrical structures and the homodesmotic reaction method to calculate the enthalpies of formation. Detonation properties and stabilities were also studied. Generally speaking, ITDOs and OTDOs have more preferable stabilities than TTDOs or pyrazolo-TDOs. I3, I4, O1, and O2 were found to be comparable to the energy level of RDX; O5 and O6 are even as powerful as HMX. The stabilities analysis in this paper can also prove that the five-membered ring deformation and the steric hindrance change caused by the different substituents will affect the stabilities of the structures of 1,2,3,4-tetrazine 1,3-dioxides annulated with a five-membered nitrogen-rich heterocycle. Other factors, such as the position of the electron-withdrawing substituents or the position of coordinated oxygen atom, are worthwhile to investigate in future work. [ABSTRACT FROM AUTHOR]