We have investigated eleven density functionals, including LDA, PBE, mPWPW91, TPSS, B3LYP, X3LYP, PBE0, O3LYP, B97-1, MPW1K, and TPSSh, for their performances on describing hydrogen bond (HB) interactions. The emphasis has been laid not only on their abilities to calculate the intermolecular hydrogen bonding energies but also on their performances in predicting the relative energies of intermolecular H-bonded complexes and the conformer stabilities due to intramolecular hydrogen bondings. As compared to the best theoretical values, we found that although PBE and PBE0 gave the best estimation of HB strengths, they might fail to predict the correct order of relative HB energies, which might lead to a wrong prediction of the global minimum for different conformers. TPSS and TPSSh did not always improve over PBE and PBE0. B3LYP was found to underestimate the intermolecular HB strengths but was among the best performers in calculating the relative HB energies. We showed here that X3LYP and B97-1 were able to give good values for both absolute HB strengths and relative HB energies, making these functionals good candidates for HB description.

Glycine conformers were investigated with three density functional theory (DFT) methods (B3LYP, PBE1PBE, X3LYP), and the second order Moller-Plesset perturbation theory (MP2) combined with basis sets of 6-31+ G*, aug-cc-pVDZ, and aug-cc-pVTZ. Solvation effects were considered by using polarizable continuum model. Results from B3LYP and X3LYP were in generally good agreement with those of MP2, while PBE1PBE was shown to be inferior for the description of conformational potential energy surfaces. Conformers Ip, IIp, IIn, IIIp, IIIn, and IVn were all found to be low-lying states within 2.0 kcal/mol, with Ip being the global minimum in gas phase. Solvation effects can significantly change the nature of the conformational surfaces of glycine. A proper description of conformational equilibrium demands for a good treatment of both longrange and short-range solute-solvent interactions.National Natural Science Foundation of China [20525311, 20533030, 10774126, 20433030]; Ministry of Science and Technology [2004CB719902, 2007CB815206]; Research Grants Council of Hong Kong SAR Governmen

Microplastics and polycyclic aromatic hydrocarbons (PAHs) were investigated to study the influence of human activities and to find their possible relationship on the coastal environments, where the coastal areas around Xiamen are undergoing intensive processes of industrialization and urbanization in the southeast China. The abundance of microplastics in Xiamen coastal areas was 103 to 2017particles/m in surface seawater and 76 to 333 particles/kg in sediments. Concentrations of dissolved PAHs varied from 18.1 to 248ng/L in surface seawater. The abundances of microplastics from the Western Harbor in surface seawater and sediments were higher than those from other areas. Foams were dominated in surface seawater samples, however, no foams were found in sediments samples. The microscope selection and FTIR analysis suggested that polyethylene (PE) and polypropylene (PP) were dominant microplastics. The cluster analysis results demonstrated that fibers and granules had the similar sources, and films had considerably correlation with all types of PAHs (3 or 4-ring PAHs and alkylated PAHs). Plastic film mulch from agriculture practice might be a potential source of microplastics in study areas. Results of our study support that river runoff, watershed area, population and urbanization rate influence the distribution of microplastics in estuarine surface water, and the prevalence of microplastic pollution calls for monitoring microplastics at a national scale.