Journal of Theoretical and Computational Chemistry

Based on the new accurate potential energy surface of the ground state of LiH₂ system. Quasi-classical trajectory (QCT) calculations were carried out for the reaction LiH + H. The reaction probability of the title reaction for J = 0 has been calculated. The reaction cross sections were calculated as functions of the collision energy in the range 0.1–2.5 eV. The results were found to be well consistent with the previous real wave packet (RWP) and QCT results.

The energetically favorable structures and characteristic infrared (IR) and Raman peaks of Ti_nO_m(n = 2–4, m ≤ 2n) clusters are obtained in this work using a B3LYP/6-311G(d) method of density functional theory (DFT). The structures with m < 2n compose of Ti atoms of lower numbers of coordination with O atoms, providing many dangling bonds which considerably enhance the reactivity compared with its bulk counterpart. Two- and three-coordinated O atoms present for m/n ≤ 1.5, whereas two- and also single-coordinated O atoms are found for m/n > 1.5. The Ti_nO_m(n = 2–4, m < 2n) clusters show strong IR peaks in the range of 600–1100 cm^-1 and strong Raman peaks in the region of 300–800 cm^-1, whereas both the IR and Raman spectrum peaks of the Ti_nO_m(n = 2–4, m = 2n) clusters are in the region of 700–1100 cm^-1. The main Raman peak of the Ti_nO_m(m ≠ 2n) clusters is at a frequency considerably lower than that of the IR spectrum. Our results can help understand the structure-property relationships of the Ti_nO_m clusters and provide their characteristic spectroscope features for further experimental identification.

The cyano (–CN), isocyano (–NC), nitramine (–NNO₂), and nitrate (–ONO₂) derivatives of HNS has been studied in this work at the B3LYP/6-31G* level of density functional theory. Their IR spectra were predicted and assigned by vibrational analysis. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic functions were evaluated. It is found that the thermodynamic functions linearly increase with the number of –CN, –NC, –NNO₂, and –ONO₂ groups, as well as the temperature. The contribution of various substitutents to the thermodynamic functions has the order of –ONO₂ > –NNO₂ > –NC > –CN. Detonation properties were evaluated using the modified Kamlet–Jacobs equations based on the calculated densities and heats of formation. Compared with the commonly used explosives (RDX and HMX), 3,3′,5-trinitramine-2,2′,4,4′,6,6′-Hexanitrostilbene, 3,3′,5,5′-tetranitramine-2,2′, 4,4′,6,6′-Hexanitrostilbene, 3,3′,5-trinitrate-2,2′,4,4′,6,6′-Hexanitrostilbene, and 3,3′,5,5′-tetranitrate-2,2′, 4,4′,6,6′-Hexanitrostilbene have better detonation performance and may be potential candidates of high energy density compounds.

The molecule 5-methyltetrazole (5MTZ) can exist in two taumeric forms. The vertical ionization energies (VIEs) of both valence and core electrons of both the tautomers are calculated with our established DFT procedures and compared with available experimental data. For the 2H-tautomer, the average absolute deviations (AADs) for the outer-valence VIEs and core-electron binding energies (CEBEs) from experiment are below 0.1 eV, while the AAD for the inner-valence VIEs is much larger at 0.4 eV. For the 1H-tautomer, no observed valence VIEs have been reported and the AAD for the calculated CEBEs is 0.2 eV. The assignment of the experimental core-electron ionization spectrum is confirmed, but our results suggest a slight modification of the assignment of the UV photoelectron spectrum of the 2H-tautomer.

We carried out systematic density functional theory computations to search for new members of C₇₀ homofullerenes inspired by the Bent's rule. By substituting CH₂ by CF₂, we identified five experimentally accessible C₇₀ homofullerenes, among which one member has different bonding character as its CH₂ counterpart (where the closed three-membered ring is formed by CH₂ addition). This unique C₇₀ homofullerene is expected to be synthesized very smoothly using the standard solution phase chemistry, due to its high thermodynamic stability and the rather high local reactivity of the carbon bond attached to the CF₂ addend.

By numerically solving the three dimensional time-dependent Schrödinger equation, we explore the high-order harmonic and attosecond pulse generation of He atoms exposed to a special three-color field. An ultrabroad supercontinuum with a bandwidth of 887 eV has been attained, supporting an isolated 4 as pulse straightforwardly by Fourier transforming. Utilizing available intense infrared femtosecond laser resource within the nonrelativistic regime, the produced laser pulse is near to zeptosecond region. Remarkably, the harmonic conversion efficiency is enhanced in terms of the double-plateau structure of the harmonic spectra, yielding high-intensity attosecond pulses with alternative plateau.

A number of charge transferring molecules with varying electron donor, acceptor and π-conjugative paths have been considered for the theoretical study of their NLO properties in terms of the linear polarizability and the ground state dipole moment. The equilibrium structures are calculated at the HF, MP2 and B3LYP levels, respectively. The longitudinal components of NLO coefficients are calculated by using HF, MP2, B3LYP, BHHLYP, CAM-B3LYP, and wB97XD methods for 6-31+G(p,d) and 6-311++G(p,d) basis sets. The hyperpolarizabilities obtained at different levels of calculation showed a fairly consistent trend. The relationships between hyperpolarizabilities, polarizability and ground state dipole moment have been proposed by considering only the two-level term in the standard sum-over-state (SOS) expressions and the generalized Thomas–Kuhn (TK) sum rule. The ab initio calculated first- and second-hyperpolarizabilities fairly correlate with the reduced 2-level contributions relating to the linear polarizability and ground state dipole moment. For a given length of conjugation the stronger enhancement of cubic polarizability arises from the increase of quadratic polarizability for comparable values of linear polarizability and dipole moment. The idea developed in the present work can be used to make a rational design of potential NLO-phores.

Poly (para-phenylene)s (PPP) and polypyrroles (PPy) are important members of the conducting polymers. Rod–coil type diblock copolymers formed by coupling of PPP and PPy rigid blocks with polycaprolactone (PCL), polystyrene (PS) and polymethylmethacrylate (PMMA) coil blocks were modeled and morphological properties have been studied by a coarse grained simulation method at the mesoscale. Geometry optimizations and the atomic charge calculations were done quantum mechanically to obtain the input parameters for the mesoscale dynamics simulations. The accurate mixing energies and the Flory–Huggins interaction parameters between the monomers of polymers were calculated and used to study the phase behaviors and the morphologies of the copolymers as a function of type and weight percentages of the blocks by Dissipative Particle Dynamics (DPD) simulations. We showed that the methodology employed took into account not only the interaction parameter and chain length of the blocks but also the chemical structure of the polymers and it could be used to produce the phase diagram of the copolymers which has importance for the industrial applications of such materials. Among the studied copolymers, the most suitable one for thin layer applications was predicted to be PPP–b–PCL in which PPP forms lamellar and cylindrical phases in the PCL matrix if amount of PPP rod block is below 50 wt%.

The mechanism of the reaction CF₃CHFO₂ + NO was investigated using ab initio and density functional theory (DFT). The optimized geometries for all stationary points on the reaction energy surface were calculated using MP2 and B3LYP methods with the aug-cc-pVDZ basis set. Single-point energy calculations were performed using the coupled cluster method with single, double and perturbative triple configurations, CCSD(T). The most important energy minima on the potential energy surface (PES) were found corresponding to two conformers of the peroxynitrite association adducts, cis-CF₃CHFOONO and trans-CF₃CHFOONO, and the nitrate, CF₃CHFONO₂. The radical pairs (CF₃CHFO + NO₂) and the nitrate are formed through the breaking of the peroxy bond of trans-CF₃CHFOONO and the rearrangement of cis-CF₃CHFOONO, respectively. The nitrate can be decomposed to carbonylated species (CF₃CHO or CF₃CFO), nitryl fluoride (NO₂F), nitrous acid (HONO), and radical pairs (CF₃CHFO + NO₂), which are of potential atmospheric importance.

The structures and electronic properties of different Co₂P-supporting configurations on the rutile TiO₂(110) surface have been investigated by first-principles density functional theory (DFT) calculations. A number of possible structural candidates and adsorption sites have been considered, while the calculations are executed on periodic systems using slab model. Our results indicate that the O atoms on TiO₂(110) turn out to be preferable for the cluster to adsorb by Co atoms, with the largest adsorption energy of 211.50 kJ/mol in the most favorable model. According to the Mulliken charge analysis, the Co₂P cluster carries a significant positive charge after adsorption, due to the charge transfer occurring from the adsorbate to the substrate. Moreover, the frontier molecular orbital analysis shows that the cluster-surface binding occurs mostly through the interplay of filled Co 3d orbital with unoccupied eigenstates of surface localized on O 2p orbital, which can be also corroborated by the projected density of states investigations, while the lowest unoccupied molecular orbital is mostly contributed by Ti 3d orbital of the surface. In addition, of particular significance is that deposition of Co₂P on the rutile TiO₂(110) surface results in a small band gap narrowing vis-à-vis the pure surface, yielding a positive effect on catalytic activity.

In this study, the drastic influence of the boron atom on the acidity of alcohol has been considered. The calculated ΔH_acid (320.9–338.1 kcal/mol) and pK_a range of boron containing alcohol (-0.1–9.4) indicate that the boronation of alcohol leads to considerable enhancement of its acidity. For instance, we have obtained the ΔH_acid values 338.1, 335.2 kcal/mol and the pK_a values 4.12, 2.81 for BH₂CH₂OH, BF₂CH₂OH alcohols, respectively, which are much smaller than that of CH₃OH (with ΔH_acid = 374.9 kcal/mol and pK_a = 15). The increase in the acidity of boronated alcohol can be related to the stabilization of alkoxy ion due to overlap of unoccupied orbital of boron atom with the electron pairs of negative oxygen. All gas phase computations were performed at MP2/6-311++G(d,p)//(B3LYP/6-31+G(d)) level. The primary results indicate that the presence of boron atom in an alcohol might make it as acidic as nitric acid. The geometry optimization of studied structures was performed with DFT computation and optimized structures were used to carry out natural bond orbital (NBO) analysis. NBO analysis revealed that the increase in the acidity of boron-containing alcohols is due to the charge transfer from the negative oxygen (in deprotonated structure) to the empty orbital of -BH₂ and -BF₂. Quantum theory of atoms in molecules (QTAIM) was also applied to determine the nature of bonds formed in the deprotonated structure.

Quasiclassical Trajectory (QCT) calculation for O(³P) + HD → OH + D and O(³P) + HD → OD + H at E_col = 0.4–1.0 eV and 0.5–1.0 eV, respectively, on the lowest PES 1 ³A″ of Kuppermann et al. has been done. Distribution p(ϑ_r) of azimuthal angles between the relative velocity k of the reactants and rotational angular momentum vector j′ of either OH or OD, p(φ_r) of polar as well as dihedral angles correlating k - k′ -j′, p(ϑ_r, φ_r), and PDDCS dependent upon the scattering angle ϑ_t of either OH, or OD between k and k′ of the reactants and products, respectively, are presented and discussed. The stereodynamics and isotopic mass effects at the smallest possible collision energies 0.4 eV and 0.5 eV for OH and OD, respectively, are significantly different. The significant mass effect with quotient 1/2 of H/D, at the corresponding collision threshold may be applied for the investigation of docking mechanism, drug modification and delivery.

Very recently, the multilayer multiconfiguration time-dependent Hartree (MCTDH) method based on a decomposition of the overall Fock space in second quantization representation was proposed [Wang H, Thoss M, J Chem Phys131:024114, 2009], and they have presented demonstrative numerical example on vibrationally coupled electron transport. Followed by the thinking, the strategies of the implement of the theory to deal with multielectron dynamics with consideration coulomb interaction were discussed in detail. Some demonstrative calculations have been carried out by using the single layer MCTDHF method. The influences of the different choice way of initial condition, such as the species of basis function, the type of decomposition of the full Fock space, the choice of the spin orbitals, the number of the single particle function and so on, on the imaginary time propagation are mainly studied. The bridge between the generalized theory and the calculation application has been set up.

Thermal desorption-comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry (TD–GC × GC–HRTOF-MS) is one of the most powerful tools in analytical nanoparticle compounds. Genetic algorithm and partial least square (GA-PLS) and kernel PLS (GA-KPLS) models were used to investigate the correlation between reverse factor (RF) and descriptors for 50 nanoparticles fraction with a diameter of 29–58 nm in roadside atmosphere which obtained by TD–GC×GC–HRTOF-MS. The correlation coefficient leave-group-out cross validation (LGO-CV (Q²)) of prediction for the GA-PLS and GA-KPLS models for training and test sets were (0.761 and 0.718) and (0.825 and 0.814), respectively, revealing the reliability of these models. This is the first research on the quantitative structure-property relationship (QSPR) of the nanoparticles in roadside atmosphere using the GA-PLS and GA-KPLS.

We report exact quantum dynamics calculations of the eigenstate energy levels for the bound rovibrational states of the Ar₂Ne complex, across the range of J values for which such states are observed (J = 0–35). All calculations have been carried out using the ScalIT suite of parallel codes. These codes employ a combination of highly efficient methods, including phase-space optimized discrete variable representation, optimal separable basis, and preconditioned inexact spectral transform (PIST) methods, together with an effective massive parallelization scheme. The Ar₂Ne energy levels were computed using a pair-wise Aziz potential plus a three-body correction, in Jacobi co-ordinates. Effective potentials for the radial co-ordinates are constructed, which reveal important physical insight into the two distinct dissociation pathways, Ar₂Ne → NeAr + Ar and Ar₂Ne → Ar₂ + Ne. A calculation of the bound vibrational (J = 0) levels, computed using the Tang–Toennies potential, is also performed for comparison with results from the previous literature.