Frontiers of Chemistry in China

ISSN 1673-3495

ISSN 1673-3614(Online)

CN 11-5726/O6

   Online First

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, Volume 6 Issue 4

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Electronic band structure from first-principles Green’s function approach: theory and implementations
Front Chem Chin. 2011, 6 (4): 253-268.

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Electronic band structure is one of the most important intrinsic properties of a material, and is in particular crucial in electronic, photo-electronic and photo- catalytic applications. Kohn-Sham Density-functional theory (KS-DFT) within currently available local or semi-local approximations to the exchange-correlation energy functional is problematic for the description of electronic band structure. Many-body perturbation theory based on Green’s function (GF) provides a rigorous framework to describe excited-state properties of materials. The central ingredient of the GF-based many-body perturbation theory is the exchange- correlation self-energy, which accounts for all non-classical electron-electron interaction effects beyond the Hartree theory, and formally can be obtained by solving a set of complicated integro-differential equations, named Hedin’s equations. The GW approximation, in which the self-energy is simply a product of Green’s function and the screened Coulomb interaction (W), is currently the most accurate first-principles approach to describe electronic band structure properties of extended systems. Compared to KS-DFT, the computational efforts required for GW calculations are much larger. Various numerical techniques or approximations have been developed to apply GW for realistic systems. In this paper, we give an overview of the theory of first-principles Green’s function approach in the GW approximation and review the state of the art for the implementation of GW in different representations and with different treatment of the frequency dependence. It is hoped that further methodological developments will be inspired by this work so that the approach can be applied to more complicated and scientifically more interesting systems.

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Calculations of ionization energies and electron affinities for atoms and molecules: A comparative study with different methods
Neil Qiang SU, Igor Ying ZHANG, Jianming WU, Xin XU
Front Chem Chin. 2011, 6 (4): 269-279.

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In the present work, we examined the performance of 36 density functionals, including the newly developed doubly hybrid density functional XYG3 (Y. Zhang, X. Xu, and W. A. Goddard III, Proc. Natl. Acad. Sci, USA, 2009, 106, 4963), to calculate ionization energies (IEs) and electron affinities (EAs). We used the well-established G2-1 set as reference, which contains 14 atoms and 24 molecules for IE, along with 7 atoms and 18 molecules for EA. XYG3 leads to mean absolute deviations (MADs) of 0.057 and 0.080 eV for IEs and EAs, respectively, using the basis set of 6–311+ G(3df,2p). In comparison with some other functionals, MADs for IEs are 0.109 (B2PLYP), 0.119 (M06-2X), 0.159 (X3LYP), 0.161 (PBE), 0.162 (B3LYP), 0.165 (PBE0), 0.173 (TPSS), 0.200 (BLYP), and 0.215 eV (LC-BLYP). MADs for EAs are 0.090 (X3LYP), 0.090 (B2PLYP), 0.102 (PBE), 0.103 (M06-2X), 0.104 (TPSS), 0.105 (BLYP), 0.106 (B3LYP), 0.126 (LC-BLYP), and 0.128 eV (PBE0).

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Computational study of topological effects on intramolecular electron transfer in mixed-valence compounds
Yinxi YU, Haobin WANG
Front Chem Chin. 2011, 6 (4): 280-286.

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The constrained density functional theory (CDFT) was used to investigate the topological effects on intramolecular electron transfer processes that have been reported in previous experimental work [Inorg. Chem., 1997, 36 (22), pp 5037-5049]. The computation mainly focused on three isomers of diferrocenylbenzenes (ortho, para, and meta) and 5-substituted derivatives of m-diferrocencylbenzenes with R= NH2, Cl, CH3, CN, NO2, N(CH3)33+, and N2+. The influence of a third group R’ (R’ = NH2 and N2+) was introduced to the ortho and para isomers. The calculations were compared with the experimental results. The relation between the substituted functional groups and the effectiveness of intramolecular electron transfer was discussed on the basis of CDFT computational results.

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Theoretical study on the hydration of hydrogen peroxide in terms of ab initio method and atom-bond electronegativity equalization method fused into molecular mechanics
Chunyang YU, Lidong GONG, Zhongzhi YANG
Front Chem Chin. 2011, 6 (4): 287-299.

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In this paper, the interaction between hydrogen peroxide (HP) and water were systemically studied by atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM) and ab initio method. The results show that the optimized geometries, interaction energies and dipole moments of hydrated HP clusters HP(H2O)n (n = 1–6) calculated by ABEEM/MM model are fairly consistent with the MP2/aug-cc-pVTZ//MP2/aug-cc-pVDZ results. The ABEEM/MM results indicate that n = 4 is the transition state structure from 2D planar structure to 3D network structure. The variations of the average hydrogen bond length with the increasing number of water molecules given by ABEEM/MM model agree well with those of ab initio studies. Moreover, the radial distribution functions (RDFs) of water molecule around HP in HP aqueous solution have been analyzed in detail. It can be confirmed that HP is a good proton donor and poor proton acceptor in aqueous solution by analysis of the RDFs.

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A study of chemical reactions in coarse-grained simulations
Hong LIU, Zhongyuan LU
Front Chem Chin. 2011, 6 (4): 300-309.

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We introduce a reaction model for use in coarse-grained simulations to study the chemical reactions in polymer systems at mesoscopic level. In this model, we employ an idea of reaction probability in control of the whole process of chemical reactions. This model has been successfully applied to the studies of surface initiated polymerization process and the network structure formation of typical epoxy resin systems. It can be further modified to study different kinds of chemical reactions at mesoscopic scale.

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Self-consistent field theory and its applications in polymer systems
Dadong YAN, Tongchuan SUO, Xinghua ZHANG, Xingkun MAN, Bing MIAO
Front Chem Chin. 2011, 6 (4): 310-331.

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This review article addresses the widely used self-consistent field theory (SCFT) in interacting polymer systems. The theoretical framework and numerical method of solving the self-consistent equations are presented. In this paper, different structures of polymer can be considered, such as homopolymer, block copolymer, polydisperse polymer and charged polymer. Several systems, micro/macro phase separation, interface, self-assembly, are presented as examples to demonstrate its applications in details. Besides, the fluctuation effects are considered. The first order is Gaussian fluctuation theory, which can be used to determine the stability of the mean-field solution and predict the kinetics of unstable structure. The derivation and applications of Gaussian fluctuation theory are presented as well.

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Preparation of polymer nanoparticles, and the effect of nanoconfinement on glass transition, structural relaxation and crystallization
Rong CHEN, Dinghai HUANG
Front Chem Chin. 2011, 6 (4): 332-340.

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In this review the preparation methods of polymer nanoparticles from chemical microemulsion polymerization to physical methods such as spray-drying, freeze-drying, freeze-extracting, fast evaporation and spreading evaporation have been summarized. The influence of nanoconfinement on glass transition temperature (Tg) variation from significant or slight decrease, no evident Tg deviation, to even Tg increase, as well as possible explanations of Tg deviations were discussed. The influences of nanoconfinement or entanglement on the other properties such as structural relaxation, crystallization in polymer nanoparticle samples were also reviewed in this article.

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Surface-enhanced Raman scattering (SERS) based on surface plasmon resonance coupling techniques
Shuping XU, Yu LIU, Haibo LI, Weiqing XU
Front Chem Chin. 2011, 6 (4): 341-354.

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Surface plasmon resonance (SPR) can provide a remarkably enhanced electromagetic field around metal surface. It is one of the enhancement models for explaining surface-enhanced Raman scattering (SERS) phonomenon. With the development of SERS theories and techniques, more and more studies referred to the configurations of the optical devices for coupling the excitation and radiation of SERS, including the prism-coupling, waveguide-coupling, and grating-coupling modes. In this review, we will summarize the recent experimental improvements on the surface plasmon-coupled SERS.

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ZnO nanorod arrays: Dependence of morphology upon ammonia
Yu XIE, Dan LIU, Ming GAO, Ru TAN, Yan WANG, Dongqi YU
Front Chem Chin. 2011, 6 (4): 355-357.

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Well-aligned ZnO nanorod arrays were prepared on FTO substrate by hydrothermal method at low temperature for 5 h. The effect of ammonia on the length of ZnO nanorod was studied in detail. The resulting materials were extensively characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible absorption spectra (scatter mode). With the increase of ammonia, the length of ZnO nanorod increases.

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Molecular structure and vibrational spectra of phenobaraitone by density functional theory and ab initio hartree-Fock calculations
Ruizhou ZHANG, Xiaohong LI, Xianzhou ZHANG
Front Chem Chin. 2011, 6 (4): 358-366.

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Quantum chemistry calculations have been performed using Gaussian03 program to compute optimized geometry, harmonic vibrational frequency along with intensities in IR and Raman spectra at RHF/6-31++G** and B3LYP/6-31++G** levels for phenobarbitone (C12H12N2O3) in the ground state. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR and FT-Raman spectra. Theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions (PEDs) using MOLVIB program. A detailed interpretation of the infrared spectra of the title compound is reported. On the basis of the agreement between the calculated and observed results, the assignments of fundamental vibrational modes of phenobarbitone were examined and some assignments were proposed. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title compound have been constructed.

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10 articles