Shao Juxiang

The evaluation of bond dissociation energies for NO2 scission in nitro compounds using density functional and complete basis set methods

By using the density functional theory (B3LYP) and four highly accurate complete basis set (CBS-Q, CBS-QB3, CBS-Lq and CBS-4M) ab initio methods, the X(C, N, O)–NO2 bond dissociation energies (BDEs) for CH3NO2, C2H3NO2, C2H5NO2, HONO2, CH3ONO2, C2H5ONO2, NH2NO2 (CH3)2NNO2 are computed. By comparing the computed BDEs and experimental results, it is found that the B3LYP method is unable to predict satisfactorily the results of bond dissociation energy (BDE); however, all four CBS models are generally able to give reliable predication of the X(C, N, O)–NO2 BDEs for these nitro compounds. Moreover, the CBS-4M calculation is the least computationally demanding among the four CBS methods considered. Therefore, we recommend CBS-4M method as a reliable method of computing the BDEs for this nitro compound system.

Potential energy surfaces of ozone in the ground state

Equilibrium parameters of ozone, such as equilibrium geometry structure parameters, force constants and dissociation energy are presented by CBS-Q ab initio calculations. The calculated equilibrium geometry structure parameters and energy are in agreement with the corresponding experimental values. The potential energy function of ozone with a C2v symmetry in the ground state is described by the simplified Sorbie–Murrell many-body expansion potential function according to the ozone molecule symmetry. The contour of bond stretching vibration potential of an O3 in the ground state, with a bond angle (�) fixed, and the contour of O3 potential for O rotating around O1–O (R1), with O1–O bond length taken as the one at equilibrium, are plotted. Moreover, the potentials are analysed.

Computation of Bond Dissociation Energies for Removal of Nitrogen Dioxide Groups in Certain Aliphatic Nitro Compounds

Bond dissociation energies for removal of nitrogen dioxide groups in 10 aliphatic nitro compounds, including nitromethane, nitroethylene, nitroethane, dinitromethane, 1-nitropropane, 2-nitropropane, 1-nitrobutane, 2-methyl-2-nitropropane, nitropentane, and nitrohexane, are calculated using the highly accurate complete basis set (CBS-Q) and the three hybrid density functional theory (DFT) methods B3LYP, B3PW91 and B3P86 with 6-31G** basis set. By comparing the computed bond dissociation energies and experimental results, we find that the B3LYP/6-31G** and B3PW91/6-31G** methods are incapable of predicting the satisfactory bond dissociation energy (BDE). However, B3P86/6-31G** and CBS-Q computations are capable of giving the calculated BDEs, which are in extraordinary agreement with the experimental data. Nevertheless, since CBS-Q computational demands increase rapidly with the number of containing atoms in molecules, larger molecules soon become prohibitively expensive. Therefore, we suggest to take the B3P86/6-31G** method as a reliable method of computing the BDEs for removal of the NO2 groups in the aliphatic nitro compounds.

High Refractive Index without Absorption in a Ladder-Type System

A three-level ladder-type system with vacuum-induced coherence and incoherent pumping is studied to obtain a high refractive index without absorption. It is shown that the enhancement of the refractive index without absorption can be accomplished by choosing the proper values of the incoherent pumping, the angle between the two dipole moments, the probe detuning and the relative phase of the two coherent fields.

Potential Energy Surfaces of Nitrogen Dioxide for the Ground State

The potential energy function of nitrogen dioxide with the C2v symmetry in the ground state is represented using the simplified Sorbie–Murrell many-body expansion function in terms of the symmetry of NO2. Using the potential energy function, some potential energy surfaces of NO2(C2V, 2A1), such as the bond stretching contour plot for a fixed equilibrium geometry angle θ and contour for O moving around N–O (R1), in which R1 is fixed at the equilibrium bond length, are depicted. The potential energy surfaces are analysed. Moreover, the equilibrium parameters for NO2 with the C2v, Cs and D8h symmetries, such as equilibrium geometry structures and energies, are calculated by the ab initio (CBS-Q) method.