Zhengyu Zhou

Studies on density functional theory for the electron-transfer reaction mechanism between M–C6H6 and M+–C6H6 complexes in the gas phase

Density functional theory (DFT) is used to theoretically investigate the electron-transfer (ET) reactions between M (Li, Na, Mg)–C6H6 and M+–C6H6 complexes in the gas phase. The geometry optimization of the metal–benzene complexes and the encounter state in the process of ET reaction was performed at the 6-31G basis set level. The metal atoms (or metal ions)–benzene molecule separation distances computed using DFT method were found to agree with second-order Moller–Plesset (MP2) results. The precursor complex has C6 symmetry, the distances between acceptor and donor is about 3.0–3.6 A, which yields a bonding energy of approximately 0.9–1.5 eV. It shows there are relatively strong interactions between them. Additionally, the geometry of transition state is also obtained by the linear coordinate method. From the analysis of the charge on the transition state and the isolated state, the reaction mechanism was derived. Also the activation energy and the coupling matrix element of the rate constant of the ET reaction are calculated. According to the reorganization energy of the ET reaction, the values obtained from George–Griffith–Marcus (GGM) method (the contribution only from diagonal elements of force constant matrix) are larger than those obtained from Hessian matrix method (including the contribution from both diagonal and off-diagonal elements), which suggests that the coupling interactions between different vibrational modes are important to the inner-sphere reorganization energy for the ET reactions in gaseous phase.

Density functional theory study of vibrational spectra of acridine and phenazine.

Density functional theory (DFT) calculations using Beckes exchange in conjunction with Lee-Yang-Parrs correlation functionals (BLYP), Beckes three-parameter hybrid DFT/HF method using Lee-Yang-Parrs correlation functionals (B3LYP) and ab initio Hartree-Fock (HF) method have been carried out to investigate the structure and vibrational spectra of acridine and phenazine. Structural parameters obtained by B3LYP/6-31G* geometry optimization are in good agreement with available experimental data. The raw BLYP non-CH stretching frequencies approximate the experimental results much better than the HF results with the mean absolute deviation about 16 cm(-1). The scaled B3LYP frequencies are more reliable than that of the BLYP and HF methods with the mean absolute deviation about 17 cm(-1). On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined. Also the structure and vibrational frequencies are compared with those of anthracene, pyridine and benzene to study the similarities and differences.

Structures and vibrational frequencies of pyruvic acid: density functional theory study

Abstract Density functional theory BLYP (using Beckes exchange and Lee–Yang–Parrs correlation functionals ), ab initio Hartree–Fock (HF) and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of pyruvic acid. Molecular conformation calculations were made for two possible conformers (eclipsed and staggered of C4O8 bond with respect to the methyl group) of the compound. Calculated results show that the stable conformer of pyruvic acid is the eclipsed one. The raw BLYP and B3LYP frequencies approximate the experimental results much better than the Hartree–Fock results, the scaled B3LYP results are more reliable than that of the BLYP and HF methods with the mean absolute deviation about 12.3 cm −1 . On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined.

Vibrational analysis for multi-channel decomposition reactions of o-pyridyl radical based on DFT methods.

The decomposition reaction pathways of o-pyridyl were investigated extensively at the B3LYP/6-311G** level. With the relative energies after zero-point energy correction, the potential energy surface was drawn out. The vibrational frequencies for all species were predicted and the reaction mechanism was elucidated utilizing vibrational frequencies and vibrational mode analysis. The primary products of o-pyridyl decomposition reactions are acetylene and cyanoacetylene.

Reaction mechanism for the F+CH2CO reaction system based on density functional theory and vibrational mode analysis

Abstract On the basis of full optimizations for all species involved F+CH2CO reaction system using Gaussian 94 package at B3LYP/6-311++G** level, the reaction mechanism is studied extensively. The potential energy surface is drawn out. With vibrational mode analysis and the electron population analysis, we proved that the main products are CO+CH2F, and the main reaction channel is F+CH2CO→CH2FCO→TS1→CO+CH2F.

Theoretical investigation of the reaction mechanism and properties for F+H2→HF+H reaction

Abstract The structures and properties of the electron transfer (ET) system for the F+H 2 →HF+H reaction are studied using five methods: UHF, UMP2, UBLYP, UB3LYP and UB3P86 at the 6-311+G ∗∗ basis set level. First, the geometry optimization of the precursor complex showed the attacking mode of the F atom. Through the analysis of the net charge, vibration mode and vibration frequency, the reaction mechanism and the process of ET are discussed. Finally, the rate constant was obtained through the calculation of the electron coupling matrix H if , inner-sphere reorganization energy λ , and activation free energy Δ G # .

Density functional theory study on the structure and vibrational spectra for 4-methyl-3-pentene-2-one

Density functional theory BLYP (using Beckes and Lee–Yang–Parrs correlation functionals), ab initio Hartree–Fock (HF) and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of s-cis-4-methyl-3-pentene-2-one. Molecular conformation calculations were made for four possible conformers of the compound using the HF and BLYP methods. Calculated results show that: (1) the stable conformer of the 4-methyl-3-penten-2-one is s-cis; (2) the BLYP/6-31G∗ and scaled HF/6-31G∗ frequencies correspond well with each other and with available experimental assignment of the normal vibrational modes.

Investigation on mechanism of the decomposition reaction of CH3OF with vibrational mode analysis

All species involved in the multi-channel decomposition reaction of CH(3)OF have been investigated using density functional theory. The molecular geometries for various species are optimized employing B3LYP method implementing 6-311++G** basis set. The potential energy surface is drawn out for this reaction. The vibrational mode analysis is used to elucidate the relationships of the transition states, intermediate and the products. The extensive investigation shows that the reaction mechanism is reliable.

Theoretical investigation of the conformation for 2-butanimine

The molecular structure and conformational stability of 2-butanimine have been investigated using ab initio and density functional theory methods. The molecular geometries for various conforms are optimized employing MP2, BLYP, and B3LYP methods implementing 6-311++G∗∗ basis sets. From the calculations, the molecules are predicated to exist in four stable conformers with the (E)-sp form being slightly lowers in energy than the other ones. The vibrational frequencies for the four conforms are computed at different levels and compared to the fundamental values. The results indicate that B3LYP frequencies reproduce the experimental values satisfactorily. On the basis of the comparison between calculated and experimental results, the fundamental vibrational modes are assigned. Through the analysis of the vibrational modes and frequencies for the four conformers, we can conclude that the vibrational quantum number ν is a crucial variable to get reasonable energy difference between various conformations.

Theoretical studies on O(3P)+CH2Cl reaction mechanism

Abstract The reaction of oxygen atom with chlorinated methyl radical has been studied using density functional theory (DFT) method at 6-311++G ∗∗ level. All the geometries, vibrational frequencies and energies of different stationary points are calculated by B3LYP/6-311++G ∗∗ and the results agree with the experimental values. The vibrational frequencies and modes of the reactant, intermediates, transition states and products have been calculated, the changes of these frequencies and modes analyzed and the changes in the vibrational force constants are assigned. The relationship and the change among them can confirm the mechanism of the reaction and the process of electron transfer. Through the analysis, the major and minor reaction channels are confirmed. A new study method of analyzing reaction mechanism is presented.