The proton exchange membrane fuel cell (PEMFC) is an innovative technology for the realization of next-generation power sources, in which a polymer or blend membrane is used to separate the fuel from the oxidant and to transport protons. Although a variety of membranes have been synthesized and characterized by both experimental and molecular simulation methods in the past few decades, the underlying microscopic molecular mechanism is still unclear. In this article, a blend membrane composed of SPEEK and PVDF is investigated by dissipative particle dynamics (DPD) and molecular dynamics (MD) simulation methods. The results show that the blend of SPEEK and PVDF has preferable compatibility as the sulfonation degree is about 50%, and the compatibility is improved further by adding 10% PSSA grafting additive. For both 90/10 and 80/20 blending proportions, SPEEK and PVDF-g-PSSA mixed fairly well, and a proton exchange channel network is observed. What's more, as the PVDF-g-PSSA content increases from 5% to 20%, the hydrophilic clusters, which consist of sulfonate groups, water molecules and hydronium ions, are formed and aggregate inside the SPEEK membrane. In addition, the transport properties and proton conductivities of the blend membrane are also significantly improved by the increase of the content of PVDF-g-PSSA.

Correction for ‘Dissipative particle dynamics and molecular dynamics simulations on mesoscale structure and proton conduction in a SPEEK/PVDF-g-PSSA membrane’ by Yue Ma et al., RSC Adv., 2017, 7, 39676–39684.

The linear and nonlinear optical properties of MnHg(SCN)4 (MMTC) single crystal are studied by the Density Functional Theory (DFT) method. The optimized lattice constant can be compared with the experimental value. The DFT method is used to calculate the hyperpolarizability of MMTC single crystal and the second harmonic generation coefficient is studied by the ionic group theory. The obtained second harmonic generation coefficient is d15=17.14–25.91 pm/V, which is in agreement with the experimental result (19.8–28.8 pm/V). It is found that the greatest contribution for the second harmonic generation of MMTC crystal is from HgS4 anionic group.

The ground- and excited-state structures of [AuS2PH2]2 are optimized by the MP2 and CIS methods, respectively. The calculated Au–Au distances of [AuS2PH2]2 indicate the presence of metallophilic attraction between the two Au atoms, which is weak in the ground state structure (Au–Au distance: 3.073 Å) but greatly enhanced in the lowest-energy triplet excited-state structure (Au–Au distance: 2.716 Å). On the basis of the MP2- and CIS-optimized structures, the TD-DFT method is employed to calculate the spectra of [AuS2PH2]2 and the results show that [AuS2PH2]2 possesses the 1,3[dσ∗(Au)sσ(Au)] lowest-energy excited states. In the luminescence, the Au–Au interaction plays a key role and the strong Au–Au interaction can result in a red shift to the visible region.

The crystal growth, space group, Raman and IR spectra of the thiocyanato manganese mercury-N,N-dimethylacetamide (MnHg(SCN)4(H2O)2 (C4H9NO)2, MMTWD) single crystal are introduced. The experiments show that the characteristic vibrational modes of MMTWD crystal consists of eight frequency regions: 50–300 cm−1, lattice modes; 300–550 cm−1, NCS bending; 550–700 cm−1, H2O wresting; 700–1200 cm−1, SCN stretching; 1200–1400 cm−1, CH3 bending; 1400–1500 cm−1, OH bending; 1500–1700 cm−1, CH2 bending or CO stretching; 2000–3400 cm−1, CN, CH, and OH stretching. Spectra analysis reveals that MMTWD crystal belongs to the two-dimensional layer net structure. The complex network layers are piled up in the c axis direction, and the water and dimethylacetamide (C4H9NO, DMA) molecules occupy the interlayer space. It is the additive and coordinates of water and DMA molecules in the layers that provides the crystal with large interaction force between molecules within a layer, which in turn, induces large nonlinear optical properties and higher environmental stability.

The periodic molecular structure model of solvent-asphaltene system is constructed using molecular mechanical and molecular dynamical methods. The influences of six kinds of different solvents (Nitrobenzene, Quinoline, Pyridine, 1-methylnaphthalene, Dibromomethane, Benzene) on the aggregate process of asphaltene molecules are investigated at normal temperature and higher temperatures. According to the analyses of structure and energy, the main interaction for the asphaltene aggregate is determined, and the influencing mechanism for the asphaltene stability in different solvent is discussed at 300 K and 573 K temperatures. It is found that van-der-Waals (VDW) interaction plays an important role in the stability of the asphaltene aggregate. The electrostatic interaction is small compared to the VDW interaction, and the π-π interaction is the leading force for the aggregation of asphaltene molecules. The presence of heteroatom might be the major reason for the asphaltene polymerization. Benzene and nitrobenzene have a prominent inhibiting or disaggregation effect on the asphaltene aggregation, and they can be chosen as inhibiting and scavenging agents.

The periodic molecular structure model of solvent-asphaltene system is constructed using molecular mechanical and molecular dynamical methods. The influences of six kinds of different solvents (Nitrobenzene, Quinoline, Pyridine, 1-methylnaphthalene, Dibromomethane, Benzene) on the aggregate process of asphaltene molecules are investigated at normal temperature and higher temperatures. According to the analyses of structure and energy, the main interaction for the asphaltene aggregate is determined, and the influencing mechanism for the asphaltene stability in different solvent is discussed at 300 K and 573 K temperatures. It is found that van-der-Waals (VDW) interaction plays an important role in the stability of the asphaltene aggregate. The electrostatic interaction is small compared to the VDW interaction, and the π-π interaction is the leading force for the aggregation of asphaltene molecules. The presence of heteroatom might be the major reason for the asphaltene polymerization. Benzene and nitrobenzene have a prominent inhibiting or disaggregation effect on the asphaltene aggregation, and they can be chosen as inhibiting and scavenging agents.