The Weak Interaction on CO_2...CO van der Waals Complex: A Theoretical Study

The geometries of van der Waals complex CO 2...CO were optimized at DFT and second order Moller Plesset perturbation(MP2) levels with the large basis set, three stable structures were found. The most stable structure has a T shape geometry in which the CO lies along the C 2 axis of CO 2, with the two C atoms direct contact and R (C...C)=0 3227 nm. The corresponding energies of the most stable structure were calculated by means of MP2, MP4D, MP4DQ, MP4SDTQ, MP4SDQ, CCSD and CCSD(T) methods. The BSSE(basis set superposition error) was eliminated by the Boys Bernardi counterpoise correction(CP) method. According to thermodynamics data, van der Waals complex CO 2...CO can be found at a low temperature and/or a high pressure. There is a little charge transferred between the two interacted subunits. In the most stable structure, CO 2 is the acceptor and CO is the donor.

Theoretical Study on the Long-lived Complexes for the Na +I_2Collision System

For the Na+I2 collision system, theoretical study is performed on the QCISD(T) level by using ab initio method. The ab initio potential energy surfaces are got and on them the long-lived complexes are found and optimized. These results verify the crossed molecule beam experimental phenomenon and the detailed geometry structures are given for the first time. The role of the complexes in the reaction path is also described in detail.

A DFT Study on Intramolecular Hydrogen Bond in Substituted Catechols and Their Radicals

Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.

A Possible Reaction Channel from BrONO to BrNO_2

A possible isomerization channel from BrONO (bromine nitrite) to BrNO2 (nitryl bromide) is predicted by means of MP2 and QCISD(T) (single-point) methods. The channel is a direct bromine abstraction reaction from BrONO molecule by NO2 in which the forward reaction barrier is 89.30 kJ/mol at final UQCISD(T)/6-311+G(2df)//UMP2/6-311G(d) level of theory with zero-point energies included. The result can explain the available experiments very well.

Theoretical Studies on Formation Mechanism of Resonance States for Na+I_2→Na^++I_2^-System

An extended linear combination of arrangement channels-scattering wave-function(LCAC-SW) quantum scattering dynamic method combined with ab initio quantum chemical calculation was used to study the formation mechanism of the resonance states for the collinear Na+I 2→Na ++I - 2 ion-pair formation process on Aten-Lanting-Los potential energy surface. The resonance energy and the resonance width or the lifetime for the first resonance peak were calculated. The resonance can be identified as the Feshbach type and the physical interpretation is given. The geometric structure of the resonance state for the title system has been optimized.

Singlet H-cCNC-C: A Potential Interstellar Molecule

A new planar isomer of HNC3 system,H-cCNC-C,is theoretically predicted by means of B3LYP and CCSD(T) methods.The suggested species can isomerize into other five kinetically more stable isomers,which have been experimentally identified,with relatively higher reaction barriers.In view of its higher kinetic stability,we can reasonably believe that the obtained species H-cCNC-C can be experimentally observed in future studies.

The Study of One Carbon Unit Transfer from Imidazolidine to dUMP Analogue with ONIOM Theory

ONIOM quantum mechanics method is used in this paper to study one-carbon unit transfer from imidazolidine to 6-aminouracil derivates. The computation results show that this reaction can be completed via three paths owing to the three different proton transfer modes. By calculation and analysis, we can find the direct proton transfer is the preferable pathway.

Two Novel Isomers of HPS3 System

Two new isomers of HPS3 system, HP(S)S2 and HSSPS, are predicted by means of B3LYP method with 6-311++G(3df,3pd) basis set. The two isomers can isomerize into thermodynamically the most stable species HSPS2, which have been experimentally identified, with relatively higher reaction barriers. In view of their higher thermodynamical and kinetic stability and the experimental observation for HP(O)O2 and HOOPO in previous study, we can reasonably believe that the two species can be spectrosymmetrically characterized in future experiments.

Molecular Exchanging Energy of Anionic/Cationic Surfactants System on the Surface of Solution

In order to study synergism of the mixed suffactants system with molecularexchanging energy (ε), the Lennard-Jones formula has been firstly introduced to evaluate theε of the mixed system, CH3(CH2)nOSO -3 /CH3(CH2)nN+(CH3)3, directly from their molecularstructure. The comparison of the calculated and the observed results showed that this method ispractical.

On the Reaction Mechanism of Br_(2) with OCS

The reaction mechanism of photochemical reaction between Br2 (1Σ ) and OCS (1Σ ) is predicted by means of theoretical methods. The calculated results indicate that the direct addition of Br2 to the CS bond of OCS molecule is more favorable in energy than the direct addition of Br2 to the CO bond. Furthermore, the intermediate isomer syn-BrC(O)SBr is more stable thermodynamically and kinetically than anti-BrC(O)SBr. The original resultant anti-BrC(O)SBr formed in the most favorable reaction channel can easily isomerize into the final product syn-BrC(O)SBr with only 31.72 kJ/mol reaction barrier height. The suggested mechanism is in good agreement with previous experimental study.

Theoretical Study on the Ion-pair Formation Mechanism for the Li+I_2 →Li^+ + I_2^- System

For the Li + I2 →Li+ + I2- system, theoretical study has been performed on the QCISD(T) level by using the ab initio method. The collision complex in ion-pair formation process was found and optimized. These results show that the crossed molecule beam (CMB) experimental phenomenon is verified and the detailed geometry is given for the first time. A mechanism for ion-pair formation was proposed in detail. The position where the collision complex occurs affects the reaction path. Specifically, the process has threshold when the collision complex appeared before the crossing point between the covalent and ionic state potential energy surfaces. On the contrary, the process has no threshold after the crossing point. Theoretically, the title system belongs to the former case.

The Study of Alcoholysis of 1,2-Thiazetidine-l,l-dioxide with Quantum Chemical Method

The alcoholysis mechanism of 1,2-thiazetidine-1,1-dioxide with methanol, in which the relatively stable product is sulfonate ester, has been investigated by quantum chemical method. Our calculations indicate the reaction for alcoholysis of 1,2-thiazetidine-1,1-dioxide proceeds via two possible mechanisms: concerted and stepwise. In the stepwise mechanism, two possible reaction pathways can be followed while only one possible reaction pathway can be followed in the concerted mechanism.

1, 4-Pyrone Effects on O-H Bond Dissociation Energies of Catechols in Flavonoids: A Density Functional Theory Study

Through B3LYP/6-31G** calculations, the 1,4-pyrone efects on O-H bond dissociation energies (BDEs) of catechols in rings A or B of flavonoids were investigated. For the catechol in rin A, although 1,4-pyrone enlarged the conjugation system, its electron-withdrawing property increased the O-H BDE -3×4.184kJ/mol compared with that of catechol. However,for the catechol in ring B,1,4-pyrone was poorly conjugated with the moiety,and therefore, had little effect on the O-H BDE.

Quantum Chemistry Study of Hydrolysis Mechanism of 1,2-Thiazetidine 1,1-Dioxide

The hydrolysis of 1,2-thiazetidine 1,1-dioxide has been studied by using ab initio and density functional theory at HF/6-31G*, MP2/6-31G* and B3LYP/6-31G* levels, showing there exist two potential theoretical products. One is N-ethyl amino-methyl sulfonate (P1) in which breaking of bond S–C is concerted, the other is 2-taurine methyl ester (P2) which involves two reaction processes with two different mechanisms: concerted and stepwise. There are two pathways of a and b in stepwise, and the former is the lowest in energy barrier in the hydrolysis of 1,2-thiazetidine 1,1-dioxide. The energy barriers of water-assisted hydrolysis of 1,2-thiazetidine 1,1-dioxide are obviously lower than those of no-water-assisted hydrolysis. Solvent effects have been considered by means of a polarizable continuum model (PCM).

Three Novel Isomers of FCH_2CP System

Three new isomers of FCH2CP system, F(H)CCPH (1), F-cCPC-H(H) (2) and F-cCC(H)P-H (3), are predicted by means of B3LYP and CCSD(T) (single-point) methods with 6-311++G(d,p) and 6-311++G(2df,2p) basis sets, respectively. The three calculated isomers can isomerize into thermodynamically the most stable species F-cPC(H)C-H, which has been suggested in previous theoretical studies, with relatively higher reaction barriers. In view of their higher thermodynamic and kinetic stability, we believe that the three species can be detected in future experiments.

Performances of Aluminum-cobalt Co-substituted α-Ni(OH)_2 Electrodes

Aluminum\|cobalt co\|substituted \%α\%\|Ni(OH)\-2 was prepared by means of the titration method in a buffer solution,the structure was characterized by XRD analysis. With above mentioned \%α\%\|Ni(OH)\-2 as the positive electrode of a nickel\|metal hydride cell,the discharge performances were examined by constant\|current charge\|discharge experiments. In comparison with the electrodes made of aluminum substituted or cobalt substituted Ni(OH)\-2 materials,the aluminum\|cobalt co\|substituted composite electrodes possess an excellent electrochemical performance and are of practical significance.

Theoretical Studies on Electronic Spectrum Property of 2-(2-Hydroxyphenyl)pyridine Via Time-dependence Density Functional Theory Method

The geometrical structures of 2 (2 hydroxyphenyl) pyridine(PP) and its protonation states were optimized by means of the B3LYP/6 31G(d) method. For all the selected systems, the existence of H bond is in favor of the stability of the systems. On the basis of the optimized geometrical structures, their electronic spectrum properties were studied by time dependent density functional theory(TD DFT) methosd via a hybrid function of B3LYP and 6 31G(d) basis set. The TD DFT calculation result predicts the absorption spectrum of PP at 324 nm(3.82 eV), which is in very good agreement with the experimental value of 322 nm( 3.85 eV ) determined in solvent chloroform. The absorption spectra of the two protonation states both exert a red shift in various pH media.

Dynamic Study of Gemini Surfactant and Single-chain Surfactant at Air/Water Interface

Molecular dynamics (MD) simulation are used to study the properties of gemini surfactant of ethyl-α,ω-bis(dodecyldimethylammonium bromide) (C12C2C12) and dodecyl- trimethylammonium bromide (DTAB) at the air/water interface, respectively. In the two systems, the surfactant concentrations are both 28 wt. %, and other conditions are also the same. After reaching the thermodynamic equilibrium, the concentration profiles, the radial distributions functions (RDF) and the mean squared displacement (MSD) are investigated. The results reveal that the surface activity of C12C2C12 surfactant is higher than DTAB surfactant.

Dispersion of Polyacenic Semiconductor(PAS) in Polyethylene: Molecular Dynamics Simulation

The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stage, PAS particles in the crystal region of PE are expelled to the amorphous region; in the second stage, PAS particles aggregate due to small surface areas and PE chains are adjusted continuously, which makes the crystal region complete; PAS particles are separated from each other and the total energy increases in the third stage. During the whole dispersing process, PAS particles are more stable in the amorphous region than in the crystal region. All the simulation results are in good agreement with the experimental results.