Papers by Keyword: Heat of Formation

Abstract: The study involves treating various metal complexes in "gas phase" with the prepared ligands (2,6-bis (((1-octyl-1H-1,2,3-triazol-4-yl) methoxy) methyl) pyridine (L₁), 2,6-bis (((1-decyl-1H-1,2,3-triazol-4-yl) methoxy) methyl) pyridine (L₂) and 2,6-bis (((1-dodecyl-1H-1,2,3-triazol-4-yl) methoxy) methyl) pyridine (L₃). Two different types of programs, the Hyperchem-8 and Gaussian programs, were used to study the theory. The heat of formation (ΔH^of), binding energy (ΔEb), and dipole moment (µ) for free ligands and some metal complexes were calculated using semi-experimental and molecular mechanics in the Hyper-8 program using a variety of computational techniques including ZINDO/1, PM3, and AMBER methods at room temperature. The created complexes are discovered to be more stable than the free ligands. For proper location of the molecules, Hyperchem.-8 was used to determine the vibration frequencies for (FT-IR) and electronic transitions, as well as electrostatic potential, HOMO, and LUMO energy. The compatibility of the theoretical and experimental findings was highlighted. In order to calculate the geometry optimization, dipole moment (µ), total energy, electrostatic potential, LUMO, and HOMO, a Gaussian algorithm employing a semi-empirical (PM3) approach was utilized. "Vibration spectra of free ligands are calculated and noted that they agreed well with those values experimentally found" diagnosis with a higher level of capacity to effectively diagnose packages. Using a technique like ZINDO/S, the electronic transitions for the ligand were also computed.

Abstract: In this study, we investigate the effect of ternary addition on the structural, mechanical properties and temperature dependence of Ti-based as potential shape memory alloys using molecular dynamics approach. We found that binary Ti-Pt alloys exhibit shape memory properties and display possible martensitic transformation from B2 to B19 phases. Partial addition with Zr, Co, Pd, Ir showed preferential ternary high temperature shape memory alloys formation of 6.25 at. % X composition (Ti-Pt-X). We found that the equilibrium lattice constants are in better agreement with the available experimental values. The heats of formation and elastic properties reveal possible composition and phases at temperature above 900 K with good shape memory properties. Their structures were confirmed using the X-ray diffraction patterns at different temperatures.

Abstract: The study on the Ti-based materials and its application has been the interest of many research industries. These alloys are known to have an ordered B2 phase at high temperatures and transform to a stable low B19 martensitic phase. First principle approach has been used to study L1₀, B32, B2 and B19 Ti₅₀Al₅₀ alloys and the results compared well with the available experimental data. The equilibrium lattice constants are in good agreement with the experimental values (within 3% agreement). Furthermore, the elastic constants of these alloys are calculated, and revealed stability for L1₀ and B19 structures, while B2 and B32 gave C′<0 (condition of instability).

Abstract: In this study, equilibrium lattice parameters, heat of formation and cohesive energy of four kinds of typical phases with different structure intermetallic compound in Al-Cu-Mg alloy were investigated by first-principles calculations based on density functional theory via CASTEP software. The calculation results are analyzed and show that ternary strengthening phase Al₂CuMg generated first when Mg content is higher, while binary strengthening phase Al₂Cu or Al₃Cu₂ first generated and more stable when Mg content is low in Al-Cu-Mg alloy which indicates that element Cu and Al alloying capacity significantly higher than that of Mg and Al element.

Abstract: The structural properties, elastic properties, and heat of formation of a high entropy alloy (HEA) of AlCoCrCuFeNi containing different mole fraction of Ni. The calculated results indicate that the lattice parameter decreased and the mass density increased as the mole fraction of Ni increased. The high entropy solid solutions AlCoCrCuFeNi_x using the FCC model are mechanically stable. The elastic properties have been deduced by Voigt-Reuss-Hill (VRH) approximations, and the calculated ratio of shear modulus to bulk modulus indicated that When the mole fraction of Ni was 0 in the FCC model, or 0.5 in both the BCC and FCC models, the high entropy solid solutions were considered ductile materials. All the HEAs are thermodynamically stable due to their negative heats of formation.

Abstract: Computations by density functional theory (DFT) method were performed on a series of di-s-tetrazine derivatives with different substituents and linkages. The heat of formation (HOF) was predicted by designed isodesmic reaction. The results illustrated that introductions group –N₃ or –N=N– could augment the HOF extremely. The crystal structures were obtained by molecular mechanics methods with dreiding force field. Detonation performance was evaluated by using the Kamlet-Jacobs based on the calculated density and HOF. It was found that –ONO₂, –NF₂, –NH–NH– and –N=N– groups were effective to enhance the detonation performance of these derivatives. Seven compounds were screened as the potential candidates for high energy density materials.

Abstract: B3LYP /aug-cc-pvdz level of theory, combined with NBO and G3 methods, is applied to study substituent effects on the geometries, bond dissociation energies and high energetic density material properties of 27 kinds of derivatives designed by substituted hydrogen atoms of pentazine, 1,2,4,5-tetrazine and s-triazine, of which the hydrogen atoms are substituted by CN, -NO₂, -NH₂, -N₃, -N₂H, -NHNH₂, -N₄H and-N₄H₃ groups. The relatively small heats of formation are observed for the derivatives substituted by-NH₂, -H, -NO₂ and-NHNH₂. The order of heats of formation for the derivatives containing the same substituent is: pentazine > 1,2,4,5-tetrazine >s-triazine. For the derivatives substituted by-CN, -N₂H and-N₄H₃, heats of formation are 860~1124 kJ/mol,in which heats of formation of 1,2,4,5-tetrazine derivatives are larger. For derivatives substituted by-N₃ and-N₄H, their heats of formation are 974 1735 kJ/mol, which are the highest in all derivatives. The order of heats of formation is: s-triazine derivative > 1,2,4,5-tetrazine derivative > pentazine derivative. The normalized heats of formation of these pentazine derivatives substituted by-CN-N₃ ,- N₂H and N₄H and 1,2,4,5-tetrazine derivatives substituted by-CN-N₃ and N₄H are 93 109 kJ, which is higher than that of triazido-s-triazine and diazido-s-tetrazine derived from Hiskey. Our observations indicate that the higher heats of formation of substituent molecules have, the higher ones the substitutive derivatives. By means of the data of dissociation energy, it can be found that the heats of formation of derivatives substituted by N₃, -N₂H and CN are greater, and they are also more stable. It is possile for them to become energetic materials with high-energy and low sensitivity.

Abstract: The heat of formation (HOF) for a caged owurtzitane analogue compound of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane (TEX) was obtained by density functional theory B3LYP method with 6-31+G** basis set. The isodesmic reaction, instead of atomization reaction, makes good use of the available experimental data of HOFs and thus ensures the credibility of the result. The value of HOF of TEX is –448.37 kJ/mol. The predicted detonation velocity is about 8.2 km/s and detonation pressure is 31.44 GPa. The dissociation energy for the N-NO2 bond of TEX is 165.43 kJ/mol. There is large strain in TEX with strain energy of 62.47 kJ/mol. The nitro group interaction in TEX is small.