Accurate ab initio Predictions of Ionization Energies and Heats of Formation for Cyclopropenylidene, Propargylene and Propadienylidene

The ionization energies （IEs） of cyclopropenylidene （c-C3H2）, propargylene （HCCCH） and propadienylidene （H2CCC） have been computed using the CCSD（T）/CBS method, which involves the approxixnation to the complete basis set （CBS） limit at the coupled cluster level with single and double excitations plus quasi-perturbative triple excitation effect （CCSD（T））. The zero-point vibrational energy correction, the core-valence electronic correction, the scalar relativistic effect and the high level correction beyond the CCSD（T） excitations have also been made in these calculations. The CCSD（T）/CBS values for the IN（c-C3H2） and IE（HCCCH） of 9.164, 8.987 eV are in good agreement with the experimental values of （9.15±0.03） and （8.96±0.04） eV. The CCSD（T）/CBS calculations yield the IE values of 10.477 and 10.388 eV for the ionization transitions H2CCC→H2CCC^＋ （^2A1, C2v） and H2CCC→H2CCC＋ （^2A＇, Cs）, respectively. On the basis of the Franek-Condon factor consideration, the IE of （10.43±0.02） eV determined in the previous single-photon ionization experiment most likely corresponds to the ionization threshold for the H2CCC→H2CCC^＋（^2A1, C2v） transition. Although the precision of the experimental IN measurements fpr c-C3H2, HCCCH, and H2CCC is insufficient to pin down the accuracy of the theoretical calculations to better than ±30 meV, the excellent agreement between the experimental and theoretical IE values observed in the present study indicates that the CCSD（T）/CBS calculations together with high-order correlation corrections are capable of yielding reliable IE predictions for simple hydrocarbon carbenes and bi-radicals. We have also reported the heats of formation at 0 K （△H^of0） and 298 K （△H^of298）for c-C3H2/c-C3H2^＋, HCCCH/HCCCH^＋, and H2CCC/H2CCC^＋, The available experimental △H^of0 and △H^of298 values for c-C3H2/c C3H2^＋, HCCCH/HCCCH^＋ are found to be in good accord with the CCSD（T）/CBS predictions after taking into account the experimental uncertainties.

Calculation of the Heat of Formation:Ternary Alloy System

A semi-empirical calculation of the heat of formation was applied to ternary system: La-Fe-Al,Fe-Ni-V and Cu-Pd-Si.The calculated values were compared with the experimental ones and the coincidence was satisfactory.This method is helpful to predict the stabilities of ternary compounds and solid solubility.

Stability,detonation properties and pyrolysis mechanisms of polynitrotriprismanes C_6H_(6-n)(NO_2)_n (n=1-6)

To further test whether polynitriprismanes are capable of being potential high energy density materials （HEDMs）, extensive theoretical calculations were carried out to investigate on a series of polynitrotriprismanes （PNNPs）： C6H6-.（NO2）. （n=1-6） Heats of formation （HOFs）, strain energies （SE）, and disproportionation energy （DE） were obtained using B3LYP/6-311＋G（2df, 2p）//B3LYP/6-31G＊ method by designing different isodesmic reactions, respectively. Detonation properties of PNNPs were obtained by the well-known KAMLET-JACOBS equations, using the predicted densities （p） obtained by Monte Carlo method and HOFs. It is found that they increase as the number of nitro groups n varies from 1 to 6, and PNNPs with n〉4 have excellent detonation properties The relative stability and the pyrolysis mechanism of PNNPs were evaluated by the calculated bond dissociation energy （BDE）. The comparison of BDE suggests that rupturing the C--C bond is the trigger for thermolysis of PNNPs. The computed BDE for cleavage of C--C bond （88.5 kJ/mol） further demonstrates that only the hexa-nitrotriprismane can be considered to be the target of HEDMs.

Theoretical studies on a series of nitroaliphatic energetic compounds

Density functional theory calculations at the B3LYP/6-311G＊＊ level are performed to study the geometric and elec- tronic structures of a series of nitroaliphatic compounds. The heats of formation （HOF） are predicted through the designed isodesmic reactions. Thermal stabilities are evaluated via the homolytic bond dissociation energies （BDEs）. Further, the correlation is developed between impact sensitivity h50% and the ratio （BDE/E） of the weakest BDE to the total energy E containing zero point energy correction. In addition, the relative stability of the title compounds is evaluated based on the analysis of calculated Mulliken population and the energy gaps between the frontier orbitals. The calculated BDEs, HOFs, and energy gaps consistently indicate that compound 1,1,1,6,6,6-hexanitro-3-hexyne is the most unstable and the compound 3,3,4,4,-tetranitro-hexane is the most stable. These results provide basic information for the molecular design of novel high energetic density materials.

Computational studies on the structure and detonation properties of nitro-substituted triazole-furazan derivatives

Some nitro-substituted triazole-furazan derivatives are considered as potential candidates for high energy density compounds through quantum chemical treatment. Their geometric and electronic structures,band gap,thermodynamic properties and detonation properties were studied using the density functional theory at the B3 LYP /6- 311 ＋ G＊＊level. The calculated energy of explosion,density,and detonation properties of model compounds were comparable to 1,3,5-trinitro-1,3,5-triazinane（ RDX） and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane（ HMX）. The heats of formation and bond dissociation energy were also analysed to understand the nature of thermal stabilities and the trigger bond in the pyrolysis process.

Comparative DFT Study of [Mg(CHZ)_3](ClO_4)_2 and [Mg(CHZ)_3](NO_3)_2(CHZ=Carbohydrazide)

The molecular geometry,electronic structure,thermochemistry and infrared spectra of [Mg（CHZ）3]（ClO4）2 and [Mg（CHZ）3]（NO3）2 were comparatively studied using the Heyd-Scuseria-Ernzerhof（HSE） screened hybrid density functional with 6-31G＊＊ basis set.The experimental results show that the complexes have six-coordinated octahedron feature,and the metal-ligand interactions are predominantly ionic in nature.The calculated heats of formation predict that [Mg（CHZ）3]（NO3）2 is more stable than [Mg（CHZ）3]（ClO4）2.Detailed NBO analyses indicate that the ligand-anion interaction plays an important role in the stability for these two energetic complexes.Moreover,the stretching vibration frequencies of N-H bonds shift to lower wave number compared to the free CHZ ligand,which are caused by the delocalizations from N-H bond orbital to lone-pair electron antibond orbital of magnesium.

Structural,phonon,elastic,thermodynamic and electronic properties of Mg-X(X=La,Nd,Sm)intermetallics:The first principles study

We show the results of first-principles calculations of structural,phonon,elastic,thermal and electronic properties of the Mg-X inter-metallics in their respective ground state phase and meta-stable phases at equilibrium geometry and the studied pressure range.Phonon dispersion spectra for these compounds were investigated by using the linear response technique.The phonon spectra do not show any abnormality in their respective ground state phase.The respective ground states phases of the studied system remain stable within the studied pressure range.Electronic and thermodynamic properties were derived by analysis of the electronic structures and quasi-harmonic approximation.The mixed bonding character of the Mg-X intermetallics is revealed by Mg-X bonds,and it leads the metallic nature.Most of the contribution originated from X ions d like states at Fermi level compared to that of Mg ion in these intermetallics.In this work,we also predicted the melting temperature of these intermetallics and evaluated the Debye temperature by using elastic constants.

DFT Study on a Heterofullerene C_(58)Sn with Odd Number of Atoms

Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene molecule CssSn has a nearly planar tetra-coordinated Sn atom on the skeleton of cage, it is a heterofullerene molecule with odd number of atoms and a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/CEP-31G level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface, and its heat of formation was estimated in this study. Owing to the C2 symmetry of [5,6]-heterofullerene-C58Sn-C2, it is a chiral molecule.

Theoretical Studies on Property and Structure of Silacyclohexane-based Liquid Crystal Compounds

SCF-MO-AM1 calculations have been per formed on 10 silacyclohex-ane-based liquid crystal compounds by energy gradient completed optimization. The stable configurations, electronic structures, heats of formation, dipole moments and ionization potentials of titled comPounds are first reported. The calculated results are.discussed relating to the classical organic electronic theory.

Theoretical Studies on the Structure and Detonation Properties of a Furazanbased Energetic Macrocycle Compound

Based on the full optimized molecular geometric structure at 6-311＋＋G＊＊ level,the density（ρ）,detonation velocity（D）,and detonation pressure（P） for a new furazan-based energetic macrocycle compound,hexakis[1,2,5]oxadi-azole[3,4-c：3＇,4＇-e;3＇＇,4＇＇-g：3＇＇＇,4＇＇＇-k：3＇＇＇＇,4＇＇＇＇-m：3＇＇＇＇＇,4＇＇＇＇＇-o][1,2,9,10]-tetraazacyclohexadecine,were investigated to verify its capacity as high energy density material（HEDM）. The infrared spectrum was also predicted. The heat of formation（HOF） was calculated using designed isodesmic reaction. The calculation on the bond dissociation energies（BDEs） was done and the pyrolysis mechanism of the compound was studied. The result shows that the N3–O1 bond in the ring may be the weakest one and the ring cleavage is possible to happen in thermal decomposition. The condensed phase HOF and the crystal density were also calculated for the title compound. The detonation data show that it can be considered as a potential HEDM. These results would provide basic information for the molecular design of novel high energy materials.

Theoretical Analysis on Geometry Structure and Electronic Structure of LaNi_4Co

The theoretical calculation of LaNi4Co, in which Co substituted for Ni at various sites, was performed by adopting the method of total energy based on the Density Functional Theory. The augmented plane wave function was selected as a basis set in combination with Ultra-soft Pseudopotential technology. The geometry of LaNi5 was optimized and the parameters and properties of the structure were given. The theoretical results accord well with experiments. This method provides a theoretical approach for the structure prediction of such alloy. The calculations of total energy, electronic density of states and Mulliken population of LaNi4Co were carried out. The electronic structure of LaNi4Co and the change of the electronic structure due to the Co-substitution in LaNi5 alloy were analyzed from the calculated results. The stability of the alloy in which Ni was partially substituted by Co at various sites was compared and the factors controlling stability were discussed. The theoretical value of formation heat was calculated.

DFT Study on the Heterofullerene C_(48)O_(12) with Rare T_h Symmetry

The molecule with Th symmetry is rare. A novel C60-1ike molecule C48O12 with rare Th symmetry has been studied at the B3LYP/6-31G（d） level of theory. Its structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G（d） level of theory. Vibrational modes have been assigned according to their symmetry. There are 73 independent vibrational modes： 22 IR-active modes with Tu symmetry and 37 Raman-active modes with Ag, Eg and Tg symmetry, respectively. The heat of formation has been calculated by using isodesmic reactions, 765.7 kJ mol-1. According to the heat of formation and the HOMO-LUMO gap, C48O12 with rare Th symmetry is more stable than C6o.

Heterofullerenes C_(48)N_(12) and C_(48)B_(12) with Rare T_h Symmetry: a DFT Study

The molecule with Th symmetry is rare. Two C60-1ike molecules C48N12 and C48B12 with rare Th symmetry have been reported here, which is an approach to seek for the molecule with rare Th symmetry. Their structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G（d） level of theory. Vibrational modes have been assigned according to their symmetry. They all have 73 independent vibrational modes： 22 IR-active modes with Tu symmetry and 37 Raman-active modes with Ag, Eg and Tg symmetry, respectively. The heats of formation have been calculated using isodesmic reactions, and the values of C48N12 and C48B12 are 3812.0 and 3423.8 kJ mo1-1, respectively. According to the estimated band gaps for their fcc solid, they are all semiconducting materials, like C60, especially C48B12-based fcc solid.

Theoretical Study on Two C_(16)H_(12)O_4 Isomers of Derivatives of Pagodane

Two C16H12O4 isomers of derivatives of pagodane were firstly reported and studied by using DFT method. Geometries, energies, and vibrational frequencies have been calculated for the two C16H12O4 isomers with pagodane-like structures at the B3LYP/6-31G^＊＊ level of theory. Symmetries of isomer 1 and 2 are D2h and D2d, respectively. Heats of formation for the two C16H12O4 isomers have been estimated in this paper. According to the heats of formation, the two C16H12O4 isomers are more stable than pagodane. Heats of formation as well as the vibrational analysis indicate that the two C16H12O4 isomers enjoy sufficient stability to allow for the experimental preparation.

Comparative Theoretical Studies on Several Energetic Substituted Dioxin-imidazole Derivatives

The molecular structures, infrared spectra, heats of formation （HOFs）, detonation proper- ties, chemical and thermal stabilities of several tetrahydro-[1,4]dioxino[2,3-d：5,6-d＇] diimida- zole derivatives with different substituents were studied using DFT-B3LYP method. The properties of the compounds with different groups such as -NO2, -NH2, -N3, and -ONO2 were further compared. The -NO2 and -ONO2 groups are effective substituents for in- creasing the densities of the compounds, while the substitution of -N3 group can produce the largest HOF. The compound with -NO2 group has the same detonation properties as 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, while the compound with -ONO2 group has lower detonation properties than those of hexahydro-1,3,5-trinitro-l,3,5-triazine. The na- ture bond orbital analysis reveals that the relatively weak bonds in the molecules are the bonds between substituent groups and the molecular skeletons as well as C-O bonds in the dioxin rings. The electron withdrawing groups （-NO2, -N3, and -ONO2） have induc- rive effects on the linkages between the groups and molecular skeletons. In addition, re- searches show that the electronegativities of the groups are related with the stabilities of the compounds. Considering detonation performance and thermal stability, the 1,5-dinitro-2,6- bis（trinitromethyl）-3a,4a,7a,8a-tetrahydro-[1,4]dioxino-[2,3-d：5,6-d＇] diimidazole satisfies the requirements of high energy density materials.

DFT Study on Molecule C_(20)H_(10): Five Carbon-carbon Single Bonds Linking Two Pentaprismane Cages

Using geometry optimization and DFT method at the B3LYP/6-31G* level for C20H10, an equilibrium geometry is identified to have the form of polyhedral hydrocarbon with five carbon-carbon single bonds linking two pentaprismane cages. Thus, C20H10 is a tri-cage molecule with three pentaprismane cages. Vibrational frequencies and infrared spectrum are computed at the same level. The heat of formation for this molecule has also been estimated in this paper.

A Dodecahedrane-like Molecule C_(12)H_(12)B_8 with Uncommon T_h Symmetry

The molecule with Th symmetry is rare.A dodecahedrane-like molecule C12H12B8 with uncommon Th symmetry has been reported here.Density functional calculations and minimization techniques have been employed to characterize its structural and electronic properties.Its geometry,electronic properties,vibrational frequencies and heat of formation have been calculated at the B3LYP/6-311＋G（d,p） level of theory.The absence of imaginary vibrational frequency confirms that it corresponds to true minimum on the potential energy hypersurface.Its vibrational bands in the IR intensity have been discussed and compared with future experimental identification.At the B3LYP/6-311＋G（d,p） level,the heat of formation has been calculated to be 720.9 kJ mol^-1 using the isodesmic reaction.According to this value,it is a potential high energy density molecule.

DFT Study on Two C_4N_(12)O_4 Isomers with Pagodane- and Isopagodane-like Structures

Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.

Theoretical Studies on the Coplanar Dicage Pentaprismane C_(16)H_(12)

A coplanar dicage pentaprismane molecule C16H12 has been studied by using DFT at B3LYP/D95* level and ab initio method at MP2/D95* level, and the vibrational frequencies of the molecule have been calculated at B3LYP/D95* level too. The results show that the molecule is thermodynamically stable. Some physico-chemical properties, such as geometry, simulated IR spectrum and heat of formation, have been reported.

DFT Study on the Bilayer Pentaprismane C_(15)H_(10)

Using geometry optimization and DFT method at the B3LYP/6-31G* level for C15H10, an equilibrium geometry was identified to have bilayer pentaprismane formed by two pentaprismane cages sharing the same pentagon. The vibrational frequencies and infrared spectrum were computed at the same level, and the heat of formation was also estimated.