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Context: The cyano propargyl radical (CH2C3N and HC3HCN) is important reaction intermediate in both combustion flames and extraterrestrial environments such as cold molecular clouds and circumstellar envelopes of carbon stars. The acquisition of spectroscopic constants and anharmonic effect facilitates a more in-depth study of this radical. However, the data available in the literature do not allow the precise predictions for it in the interstellar medium. In this work, complete spectroscopic parameters as well as anharmonic constants of two radicals of C4H2N have been evaluated by different DFT methods. The calculated results show that it is reasonable to study the molecular spectroscopic properties of C4H2N by wB97XD/6-311++G theoretical level. On this basis, the sextic centrifugal distortion constants, anharmonic constants, vibration-rotation interaction constants, and so on are predicted for the study of high-precision rovibrational spectrum. In addition, the relationship between the anharmonic effect and vibration mode of CH2C3N and HC3HCN and their infrared spectroscopic characteristics are discussed. Methods: The calculation of the anharmonic force fields and spectroscopy properties was performed using B3LYP, B3PW91, CAM-B3LYP, and wB97XD methods combined with the 6-311++G and aug-ccpVTZ basis sets, respectively, by the Gaussian16 program suite. The IR spectra were performed with Multiwfn3.8. [ABSTRACT FROM AUTHOR]

The potential astronomical interest dithioformic acid (trans-HC(= S)SH) exists five isomers and has received considerable attention of astronomical observation in recent years. The different positions of H atoms of five isomers lead to diverse point groups, dipole moments, and spectroscopic constants. The anharmonic force field and spectroscopic constants of them are calculated using CCSD(T) and B3LYP employing correlation consistent basis sets. Molecular structures, dipole moments, rotational constants, and fundamental frequencies of trans-HC(= S)SH are compared with the available experimental data. The B3LYP/Gen = 5 and CCSD(T)/Gen = Q results can reproduce them well. Molecular structures, dipole moments, relative energies, spectroscopic constants of cis-HC(= S)SH, and dithiohydroxy carbene (DTHC) are also calculated. The new data obtained in this study are expected to guide the future high resolution experimental work and to assist astronomical search for CH2S2. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are used to investigate the aggregation of the cross-contacted and non-cross-contacted graphene sheets in n-hexane, 2,3-dimethylbutane, and cyclohexane solvents. The results show that the main driving force of the graphene aggregation is the interaction between the graphene sheets, and the interaction between solvent molecules also contributes to the aggregation slightly. The initial graphene configurations and the solvent molecule structures both have effects on the graphene aggregation speed. Specifically, the cross-contacted graphene sheets aggregate faster than the non-cross-contacted configuration, since the interaction between the graphene sheets is larger and the direction of this interaction is conducive to pushing away the solvent molecules adsorbed on the graphene surface. The graphene aggregation speed is larger in n-hexane mainly since the mobility of the solvent molecules is higher than the other two solvents, while the interaction between graphenes/solvents has little influence for the systems used in this work. This work provides useful insights into the graphene aggregation in the solvents with different initial graphene configurations and solvent molecule structures. [ABSTRACT FROM AUTHOR]

This work presents a systematic investigation of the spectroscopic properties at anharmonic force fields of ground electronic state ( X ˜ 1 A 1 ) of LiNH2, which are calculated using second-order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) with hybrid GGA and meta-hybrid GGA (M06-2X) exchange-correlation functional. Two high angular momentum basis sets of 6-311+g (2d, p) and 6-311++g (3df, 2pd) are used. The equilibrium geometries, ground-state rotational constants, harmonic frequencies, and quartic and sextic centrifugal distortion constants of LiNH2 are calculated and compared with corresponding experimental or theoretical data. The predicted accuracy of the calculated constants has been confirmed by analyzing the deviations with respect to experiment. In addition, the anharmonic constants, vibration-rotation interaction constants, force constants, and Coriolis coupling constants of LiNH2 are firstly obtained. The infrared spectrum is predicted and together with the first prediction on the higher-order anharmonic constants contributes to a better understanding of the vibrational and rotational characteristics of LiNH2, thus revealing its internal structure. [ABSTRACT FROM AUTHOR]

The equilibrium structure, spectroscopy constants, and anharmonic force field of SiF have been investigated at MP2, B3LYP, and B3PW91 levels of theory employing two basis sets cc-pVQZ and cc-pVTZ, respectively. The obtained equilibrium geometries, rotational constants, fundamental vibrational wave numbers, and centrifugal distortion constants are compared with the available experimental data or the previous theoretical values. The MP2/cc-pVQZ results of SiF are in excellent agreement with the available experimental data and afford a marked improvement over B3LYP/cc-pVQZ and B3PW91/cc-pVQZ in the calculation of spectroscopic constants and force constants of SiF. The basis set enhancement beyond cc-pVQZ does not lead to a major improvement so that the cc-pVQZ basis set is sufficient for SiF. The MP2/cc-pVQZ results may provide useful data for the spectroscopic experiment studies of SiF. The used DFT method is also an advisable choice to study anharmonic force field of SiF. [ABSTRACT FROM AUTHOR]

Cs, O activation experiment of AlGaN photocathodes was carried out and the photocurrent variation was recorded. Then first principle calculations were performed to study Cs, O coadsorption on AlGaN(0001) surface. Three surface models were built, one model represents pure surface, and the other two are defective surface models with Ga or N vacancy on the topmost layer. Cs only adsorption systems were built based on clean surface, and Cs, O coadsorption systems were built based on the three surfaces. Work function, average dipole charge, average dipole length, and dipole moments were calculated. Results show there exist double dipoles in the Cs, O coadsorbed AlGaN(0001) surfaces. One is Cs-induced dipole [Cs-AlGaN], which was caused by electrons transferring from Cs adatoms to AlGaN substrate. This dipole is perpendicular to surface, and it is helpful for electrons escaping to vacuum. The other dipole [Cs-O] is composed of Cs and O adatoms, which is induced by electrons transferring from the Cs adatoms to O adatoms. Cs, O coadsorption results in lower work function on defective AlGaN(0001) surfaces than the pure one. The reason is that the direction of [Cs-O] dipole on the defective surface is oriented to the substrate. Nevertheless, the direction difference between [Cs-O] dipole and surface without defect is too small to lower work function significantly. This work gives theoretical explanation for photocurrent variation and dipole moments formation of Cs, O coadsorbed AlGaN photocathodes. [ABSTRACT FROM AUTHOR]

The time-dependent density functional theory (TDDFT) method was performed to investigate the hydrogenbonding dynamics of methyl cyanide (MeNC) as hydrogen bond acceptor in hydrogen donating methanol (MeOH) solvent. The ground-state geometry optimizations and electronic transition energies and corresponding oscillation strengths of the low-lying electronically excited states for the isolated MeNC and MeOH monomers, the hydrogen-bonded MeNC-MeOH dimer and MeNC-2MeOH trimer are calculated by the DFT and TDDFT methods, respectively. An intermolecular hydrogen bond N≡C...H-O is formed between MeNC and methanol molecule. According to Zhao's rule on the excited-state hydrogen bonding dynamics, we find the intermolecular hydrogen bonds N≡C...H-O are strengthened in electronically excited states of the hydrogen-bonded MeNC-MeOH dimer and MeNC-2MeOH trimer, with the excitation energy of a related excited state being lowered and electronic spectral redshifts being induced. Furthermore, the hydrogen bond strengthening in the electronically excited state plays an important role on the photophysics and photochemistry of MeNC in solutions [ABSTRACT FROM AUTHOR]

The highly excited vibrational states of asymmetric linear tetratomic molecules are studied in the framework of Lie algebra. By using symmetric group U 1(4) U 2(4)⊗ U 3(4), we construct the Hamiltonian that includes not only Casimir operators but also Majorana operators M12, M13 and M23, which are useful for getting potential energy surface and force constants in Lie algebra method. By Lie algebra treatment, we obtain the eigenvalues of the Hamiltonian, and make the concrete calculation for molecule C2HF. [ABSTRACT FROM AUTHOR]