Quasi-classical trajectory (QCT) calculations for the reaction $S+H_2(v=0$-$2, j=0) → SH+H$ have been performed in order to investigate the effect of initial vibrational states on both the scalar and vector properties. The integral cross sections, opacity function have been calculated. The results indicate that the reaction probability and the cross section increase as the initial vibrational quantum number increases. The vibrational distributions and rotational distributions at different vibrational excited states are presented, and the results are discussed in detail. In addition, the vector properties, involving scattering directions of reaction product and the alignment and orientation of rotational angular momentum, are calculated and discussed. The results indicate that the vibrational excited states have a positive effect on the forward scattering direction of the product, and the vibrational excited states have slight effect on the alignment and orientation of the rotational angular momentum.

Time-dependent density functional theory (TDDFT) method has been performed to investigate the properties of $N_1$-$H_1\cdots O_1$ hydrogen bond of $N$-methylaniline-DMSO complex (complex I) and $N$-methylaniline-acetone complex (complex II) in the excited state. The infrared spectra are in good agreement with the experiment data. The analysis of the bond length and AIM (atoms in molecules) demonstrated that the $N_1$-$H_1\cdots O_1$ hydrogen bond is weakening from DMSO to acetone in the ground state. That is to say, the intermolecular hydrogen bond $N_1$-$H_1 \cdots O_1$ between $N$-methylaniline and solvent molecular is stronger with the polarity of solvent stronger. Upon photoexcitation, the analysis of AIM implies that the intermolecular complex II is enhanced. Interestingly, the hydrogen bond $N_1$-$H_1\cdots O_1$ of complex I is weakened. The analysis of molecular orbital also support the results that the intermolecular hydrogen bond $N_1$-$H_1 \cdots O_1$ of complex I is weakened whereas it of complex II is enhanced.

The equilibrium geometries of $Si_2N$ have been calculated using different quantum chemistry calculation methods. Through a large number of test and research, the method QCISD/6-31G(2d,2p) is the most suitable for the calculation of $Si_2N$ by comparing the experimental equilibrium structure and harmonic frequency data. The force constants have also been calculated. Based on the general principles of microscopic reversibility, the dissociation limits has been deduced. The analytical potential energy function of $Si_2N$ has been obtained based on the many-body expansion theory. The potential surface graphs have been presented. It's found that there is a minimum value of 4.725eV at stable structure of the potential surface and a potential well of 1.7eV correspond to the linear asymmetric structures($^2\Pi).$ And the reaction of $SiN+Si → SiNSi$ based on the potential energy surface is discussed briefly, which is successfully used for describing molecular reaction dynamics.

Three derivatives based on oligothiophenes were theoretically investigated about the electronic and charge transport properties using density functional (DFT) theory based on the Marcus-Hush theory. The predicted highest hole mobility is 0.218 $cm^2V^{-1}s^{-1},$ and the highest electron mobility is 0.373 at 300 K. The calculated data demonstrated that the compound 1 should be a high-performance $n$-type organic material candidate and compound 3 may well be potential p-type materials with high mobility values. Our work also indicates that the face-to-face $\pi$-$\pi$ interaction and $S$-$S$ interactions is favorable for the molecular stacking and charge transport behaviors. The calculated results provide an additional possibility to be able to improve the origin semiconductor performance and design new electronic devices.

We present ab initio scattering calculations results of low-energy electron collision with methylamine using $R$-matrix approach within the static-exchange (SE) and static-exchange-polarization (SEP) approximations. The elastic integral, momentum transfer and differential cross sections are reported. The calculated elastic integral cross sections are in agreement with the available experimental and theoretical data. A $σ^∗$ shape resonances of $^2A'$ symmetry located at 8.9 eV are detected within SEP model. For this dipole molecule Born-closure procedure was used to account for the higher partial waves $(l > 4)$ to obtain the convergence of the cross section.

The internally contracted multi-reference configuration interaction method (MRCI) with Davidson modification and the Douglas-Kroll scalar relativistic correction is used to calculate $BSe^+$ ion at the level of aug-cc-PVQZ basis set. The calculated electronic states, including four triple and two quintuple $Λ$-$S$ states, are correlated to the dissociation limit of $B^+(^1S_g)+Se(^3P_g)$ and $B(^2P_u)+Se+(^4S_u).$ The states of $^3\Pi$(II) and $^3Σ^-$(II) from the dissociation limit of $Se^+(^4S_u)+B(^2P_u)$ both have double well and spectroscopic properties are studied. Various curve crossing are revealed, which could lead to the predissociation of the $X^3\Pi$ and $^5\Pi$ states and the possible predissociation pathway are analyzed. Spin-orbit coupling interaction is taken into account via the state interaction approach with the full Breit-Pauli Hamiltonian operator, which causes the entire six $Λ$-$S$ states to split into 21 Ω states. This is the first time spin-orbit coupling calculation of $BSe^+.$ The potential energy curves of the $Λ$-$S$ and Ω electronic states are depicted with the aid of the avoided crossing rule between electronic states of the same symmetry. Then the spectroscopic constants of bound $Λ$-$S$ and Ω states were obtained, which have never been observed in experiment.

Several fluorescent protein fluorophores with regular substitution were investigated in gas phase using TDDFT with long range corrected functional. Absorption and emission of both neutral and anionic chromophore states were calculated. The spectral shift amplitudes of calculation are in good agreement with experiment. The further intramolecular charge transfer process analysis show that conjugated area, charge transfer number/distance and transfer efficiency can affect spectral shift. Specially, the "N" atom with lone pair electrons of conjugated ring has an important influence on charge transfer process, and the conjugated length between hydroxyl and bridge bond only impact the anionic spectral shift. Our results about fluorescent chromophore spectral red shift mechanism do provide positive clues on new experimental far-red fluorescent protein designing.

In the present work, the excited state intramolecular proton transfer (ESIPT) process between the Enol and Keto forms of the title compound has been investigated with the time-dependent density functional theory (TDDFT) method. The geometric structures, frontier molecular orbitals, electrostatic potential (ESP) maps as well as the absorption and fluorescence spectra of the two forms of the title compound have been investigated. The calculated absorption spectra of the Keto form are more in agreement with the experimental results. Moreover, the potential energy curves of the intramolecular proton transfer (IPT) within the title compound have been scanned in both ground state $S_0$ and the first excited state $S_1.$ We found that the intramolecular proton transfer from Enol form to Keto form in excited state is almost barrierless with an energy barrier 2.1 kJ/mol whereas intramolecular proton transfer between the two forms of the title compound in ground state is forbidden with energy barrier as high as 10.5 kJ/mol.