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Self-diffusion of methanol, ethanol, 1-propanol and 2-propanol has been studied by molecular dynamics simulation in the temperature range between the melting pressure curve and 478 K at pressures up to 300 MPa. The simulation results on self-diffusion of methanol, ethanol and 2-propanol (for 2-propanol, at high temperatures) agree well with experiment, which suggests that the simulation method is a powerful tool to obtain self-diffusion coefficients over wide range of temperature and pressure, under which it is rather difficult for experiments. The local structures of methanol, ethanol and 2-propanol are investigated by calculating the radial distribution functions, H-bond numbers, coordination numbers and the ratios of H-bond number divided by coordination number. The correlation between self-diffusion and structural properties, and the influence of temperature and pressure on them are discussed. The degree of forming H-bond space network in methanol, ethanol and water is higher than that in 2-propanol, and they are all higher than those in ammonia and methylamine. The simulation results demonstrate that the effect of hydrogen bonding on the translational dynamics in methanol and ethanol is more pronounced than that in 2-propanol. [ABSTRACT FROM PUBLISHER]

The various interactions occurring between pyrrole and benzene are a particularly appropriate model, as they are viewed as better X-H···π examples. A combined and sequential use of Quantum Mechanical (QM) calculations and Molecular Dynamics (MD) simulations was applied to investigate the different intermolecular interactions for benzene and pyrrole as clusters and its liquid mixture. All the cluster structures were fully optimized by the B2PLYP-D methods (including dispersion correction) with jun-cc-pVTZ (a revised aug-cc-pVTZ basis set). MD simulation with OPLS-AA force field was used to study the liquid mixture of benzene/pyrrole at different temperatures. Two types of N-H···π hydrogen bonds are preferred interactions compared with C-H···π interactions, either as clusters or as its liquid mixture. Based on the QM results, we clarify the difference in red-shifts of N-H bond of N-H···π hydrogen bonds observed by Jet FT-IR (Phys Chem Chem Phys 10: 2827, ). Meanwhile, the nature of various X-H···π interactions is unveiled by atoms in molecules (AIM), natural bond orbital and energy decomposition analysis (EDA). Furthermore, in light of QM results, MD simulation results further characterize the behavior and structural properties of these interactions. Finally, we proposed an original idea to explain the strength variation of different N-H···π hydrogen bond in liquid mixture based on AIM and EDA analysis. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A combined and sequential use of quantum mechanical (QM) calculations and classical molecular dynamics (MD) simulations was made to investigate the σ and π types of hydrogen bond (HB) in benzene-water and pyrrole-water as clusters and as their liquid mixture, respectively. This paper aims at analyzing similarities and differences of these HBs resulted from QM and MD on an equal footing. Based on the optimized geometry at ωb97xD/aug-cc-pVTZ level of theory, the nature and property of σ and π types of HBs are unveiled by means of atoms in molecules (AIM), natural bond orbital (NBO) and energy decomposition analysis (EDA). In light of the above findings, MD simulation with OPLS-AA and SPC model was applied to study the liquid mixture at different temperatures. The MD results further characterize the behavior and structural properties of σ and π types HBs, which are somewhat different but reasonable for the clusters by QM. Finally, we provide a reasonable explanation for the different solubility between benzene/water and pyrrole/water. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The possible hypochlorous acid dimers with six different configurations were found which were investigated by means of ab initio method at the MP2/aug-cc-pVTZ computational level. They were identified to be local minima, corresponding to two dimers with one O–H⋯O hydrogen bond, one dimer with one O–Cl⋯O halogen bond, one cyclic dimer with one O–H⋯Cl hydrogen bond and one O–Cl⋯Cl halogen bond, one cyclic dimer with two O–H⋯Cl hydrogen bonds, and one dimer with one O–Cl⋯Cl halogen bond. Their optimized geometries, stretching vibrational frequencies and interaction energies have been obtained and analyzed. The results show that the dimers with one O–H⋯O hydrogen bond and the cyclic one with two O–H⋯Cl hydrogen bonds are much stronger than the dimer with one O–Cl⋯O halogen bond, while the dimer with one O–Cl⋯Cl halogen bond is even weaker. AIM analysis was performed to examine the topological property of the hydrogen bond or halogen bond in the complex. The important roles of the intermolecular donor–acceptor orbital interactions as well as the charge transfer in these complexes were demonstrated by NBO analysis. Energy decomposition analyses indicate that the electrostatic, orbital and dispersion terms are the attractive interactions contributing to the stability of the complex, whereas the Pauli term is the repulsive interaction. [Copyright &y& Elsevier]

The N–H ··· π H-bond interactions of clusters and liquid formed by pyrrole molecules were investigated by Quantum Mechanics (QM) and classical Molecular Dynamics (MD), respectively. Based on the optimized geometry at the B97-D/aug-cc-pVTZ level of theory including dispersion correction, the nature and the origin of N–H ··· π H-bond interactions were unveiled by atoms in molecules (AIM), natural bond orbital (NBO), and energy decomposition analysis (EDA). Among them, the AIM analysis gives evidence to the presence of N–H ··· π H-bond interactions, the NBO examination reveals that π → σ* donor-acceptor orbital interaction is of great importance. EDA study indicates that N–H ··· π interactions are governed by the electrostatic and dispersion term. Meanwhile, MD simulation with OPLS-AA (optimized potentials for liquid simulations all-atom) was applied to study the pure liquid pyrrole at different temperature. The results confirm the existence of the N–H ··· π H-bond in the pure liquid pyrrole, and further characterized the structures of this H-bond which is somewhat different to the clusters. [ABSTRACT FROM AUTHOR]