Chemical Concepts from Density Functional Theory

Chemical concepts such as structure,bonding,reactivity,etc.have been widely used in the literature and text books to appreciate molecular properties and chemical transformations.Even though modern theoretical and computational chemistry is well established from the perspective of accuracy and complexity,how to quantify these concepts is a still unresolved task.Conceptual density functional theory and its related recent developments provide unique opportunities to tackle this problem.In this Special Issue,27 contributions from top investigators over the world are collected to highlight the state-of-art research on this topic,which not only showcases the status of where we are now but also unveils a number to possible future directions to be pursued.

Correlation of ^1H NMR Chemical Shift for Aqueous Solutions by Statistical Associating Fluid Theory Association Model

^1H NMR chemical shifts of binary aqueous mixtures of acylamide, alcohol, dimethyl sulphoxide (DMSO), and acetone are correlated by statistical associating fluid theory (SAFT) association model. The comparison between SAFT association model and Wilson equation shows that the former is better for dealing with aqueous solutions. Finally, the specialties of both models are discussed.

Analysis of marine ecological compensation for environmental risk caused by chemical spill based on game theory

The problem of marine environmental risk is ultimately the result of game theory between the marine en vironmental managers and the enterprise of potential environmental risk.This paper analyzes the internal economic relationship that whether the"protection"policy is applied between the protection action of marine environmental managers and the chemical enterprise.The result shows that the key factor whether the enterprise adopt the"protec tion"policy or not is the amount of penalty and the government's cost of execution,and the compulsive ecological compensation is obligatory from the angle of stimulating the enterprise of canonical action and adopting the"protec tion"policy.To build the ecological compensation mechanism based on the environmental risk will effectively improve the level of management in sea area and decrease the probability of chemical spill.

Solution-based Chemical Strategies to Purposely Control the Microstructure of Functional Materials

Micro/nanostructured crystals with controlled architectures are desirable for many applications in optics, electronics, biology, medicine, and energy conversions. Low-temperature, aqueous chemical routes have been widely investigated for the synthesis of particles, and arrays of oriented nanorods and nanotubes. In this paper, based on the ideal crystal shapes predicted by the chemical bonding theory, we have developed some potential chemical strategies to tune the microstructure of functional materials, ZnS and Nb205 nanotube arrays, MgO wiskers and nestlike spheres, and cubic phase Cu2O microcrystals were synthesized here to elucidate these strategies. We describe their controlled crystallization processes and illustrate the detailed key factors controlling their growth by examining various reaction parameters. Current results demonstrate that our designed chemical strategies for tuning microstructure of functional materials are applicable to several technologically important materials, and therefore may be used as a versatile and effective route to the controllable synthesis of other inorganic functional materials.

Cattaneo-Christov heat and mass flux model for 3D hydrodynamic flow of chemically reactive Maxwell liquid

This research focuses on the Cattaneo-Christov theory of heat and mass flux for a three-dimensional Maxwell liquid towards a moving surface. An incompressible laminar flow with variable thermal conductivity is considered. The flow generation is due to the bidirectional stretching of sheet. The combined phenomenon of heat and mass transport is accounted. The Cattaneo-Christov model of heat and mass diffusion is used to develop the expressions of energy and mass species. The first-order chemical reaction term in the mass species equation is considered. The boundary layer assumptions lead to the governing mathematical model. The homotopic simulation is adopted to visualize the results of the dimensionless flow equations. The graphs of velocities, temperature, and concentration show the effects of different arising parameters. A numerical benchmark is presented to visualize the convergent values of the computed results. The results show that the concentration and temperature fields are decayed for the Cattaneo^Christov theory of heat and mass diffusion.

Chemical Bond and Nonlinear Optical Effects of Crystals

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A Study of Heavy-Fermion Superconductors via BCS Equations Incorporating Chemical Potential

Heavy-fermion superconductors (HFSCs) are regarded as outside the purview of BCS theory because it is usually constrained by the inequality , where EF, μ, kB, and θD are, respectively, the Fermi energy, chemical potential, Boltzmann constant, and the Debye temperature. We show that this restriction can be removed by incorporating μ into the equations for Tc and the gap Δ0 at T = 0. Further, when μ kBθD, we curtail the limits of the equations for Tc and Δ0 to avoid complex-valued solutions. The resulting equations are applied to a prominent member of the HFSC family, i.e., CeCoIn5, by appealing to ideas due to Born and Karmann, Suhl et al., and Bianconi et al. Since the equations now contain an additional variable μ, we find that 1) the Tc of the SC can be accounted for by a multitude of values of the (μ, λ) pair, λ being the interaction parameter;2) the λ vs. μ plot has a dome-like structure when μ kBθD;3) the (μ, λ) values obtained in 2) lead to reasonable results for the range of each of the following variables: Δ0, s, and n, where s is the ratio of the mass of a conduction electron and the free electron mass and n is the number density of charge carriers in the SC.

Technologies of enhancing oil recovery by chemical flooding in Daqing Oilfield, NE China

By tracking and analyzing the research and practices of chemical flooding carried out in the Daqing Oilfield, NE China since the 1970 s, the chemical flooding theory, technology adaptability and existing problems were systematically summarized, and directions and ideas of development in the future were proposed. In enhanced oil recovery by chemical flooding, the Daqing Oilfield developed theories related to compatibility between crude oil and surfactant that may form ultra-low interfacial tensions with low-acidity oil, and a series of surfactant products were developed independently. The key technologies for chemical flooding such as injection parameter optimization and numerical simulation were established. The technologies of separation injection, cleansing and anti-scaling, preparation and injection, and produced liquid processing were developed. The matching technologies of production engineering and surface facilities were formed. Through implementation of chemical flooding, the Daqing Oilfield achieved outstanding performances with enhanced recovery rate of 12% in polymer flooding and with enhanced recovery rate of 18% in ASP flooding. To further enhance the oil recovery of chemical flooding, three aspects need to be studied:(1) fine characterization of reservoirs;(2) smart and efficient recovery enhancement technologies;(3) environment friendly, high-efficiency and smart matching processes.

A statistical model for predicting thermal chemical reaction rate

A simple model based on the statistics of individual atoms [Europhys. Lett. 94 40002 （2011）] or molecules [Chin. Phys. Lett. 29 080504 （2012）] was used to predict chemical reaction rates without empirical parameters, and its physical basis was further investigated both theoretically and via MD simulations. The model was successfully applied to some reactions of extensive experimental data, showing that the model is significantly better than the conventional transition state theory. It is worth noting that the prediction of the model on ab initio level is much easier than the transition state theory or unimolecular RRKM theory.

Electronic Structures and Chemical Bonding of NbS6^(-/0)Clusters

Density functional theory（DFT） and coupled cluster theory（CCSD（T）） calculations were employed to investigate the structural and electronic properties of Nb S6^- and Nb S6 clusters. Generalized Koopmans＇ theorem was applied to predict the vertical detachment energies and simulate the photoelectron spectra（PES）. The current study indicated that various types of sulfur ligands（i.e., S^（2-）, S^（2-）, S2^（2-） and S3^（2-）） were presented in the lowest-energy structures of Nb S6^（-/0）. The ground-state structure of Nb S6^- is shown to be Cs（~1A＇） symmetry with a terminal S^（2-）, a side-on bound S2^（2-） and a S3^（2-） ligands. Molecular orbital analyses were performed to analyze the chemical bonding in NbS6^（-/0） clusters and elucidate their structural and electronic properties.

The Algorithm of Chemical Species Analysis for Ab Intio Molecular Dynamics Simulations and Its Application

In ab initio molecular dynamics(AIMD)simulations of chemical reactions,it is important but difficult to identify the chemical species in the trajectory automatically and quickly.In this paper,based on the chemical graph theory,an algorithm for molecular species identification,according to the molecular coordinates and empirical bond length database,is presented.As an example,the chemical species in condensed glycine at room temperature are investigated with our algorithm in detail.The chemical species,including canonical and zwitterionic glycine,their protonated and de-protonated states,and the free protons,are all identified,counted and recorded correctly.Potential applications and further development of the algorithm are also discussed.

Quantum spin Hall insulators in chemically functionalized As(110)and Sb(110)films

We propose a new type of quantum spin Hall （QSH） insulator in chemically functionalized As （110） and Sb （110） film. According to first-principles calculations, we find that metallic As （110） and Sb （110） films become QSH insulators after being chemically functionalized by hydrogen （H） or halogen （C1 and Br） atoms. The energy gaps of the functionalized films range from 0.121 eV to 0.304 eV, which are sufficiently large for practical applications at room temperature. The energy gaps originate from the spin-orbit coupling （SOC）. The energy gap increases linearly with the increase of the SOC strength λ/λ0. The Z2 invariant and the penetration depth of the edge states are also calculated and studied for the functionalized films.

A theoretical study on chemical ordering of 38-atom trimetallic Pd-Ag-Pt nanoalloys

In this study,truncated octahedron(TO)structure is selected for further analysis and we focus on 38-atom Pd-Pt-Ag trimetallic nanoalloys.The best chemical ordering structures of PdnAg32-nPt6 trimetallic nanoalloys are obtained at Gupta level.The structures with the lowest energy at Gupta level are then re-optimized by density functional theory(DFT)relaxations and DFT results confirm the Gupta level calculations with small shifts on bond lengths indicating TO structure is favorable for 38-atom of PdnAg32-nPt6 trimetallic nanoalloys.The DFT excess energy analysis shows that Pd8Ag24Pt6 composition has the lowest excess energy value in common with excess energy analysis at Gupta level.In Pd8Ag24Pt6 composition,eight Pd atoms are central sites of 8(111)hexagonal facets of TO,24 Ag atoms locate on surface,and 6 Pt atoms locate at the core of the structure.It is also obtained that all of the compositions except Pd18Ag14Pt6 and Pd20Ag12Pt6 exhibit a octahedral Pt core.Besides,it is observed that there is a clear tendency for Ag atoms to segregate to the surface and also Pt atoms prefer to locate at core due to order parameter(R)variations.

Comparative Study of the Chemical Reactivity of Helical Peptide Models for Protein Glycation

Non-enzymatic glycation of proteins has been implicated as an important cause of the complications associated with diabetes and Alzheimer disease. It is well known that glycation involves the reactivity of, primarily, the ε-amino group of the lysines present in the protein. The immediate chemical environment of an amino group modulates the glycation reaction. In this work, several model helical peptides for protein glycation has been studied by resorting to QM:MM calculations through the ONIOM methodology. Some Conceptual DFT descriptors have been calculated that allowed the comparison of the chemical reactivity between the different model peptides in terms of the position of the Lys group and other spatially proximate amino acid residues.

CCSD(T) study on the structures and chemical bonds of AnO molecules (An = Bk–Lr)

The molecular geometries and dissociation energies of AnO (An = Bk–Lr) molecules were first obtained at thecoupled-cluster single-, double-, and perturbative triple-excitations [CCSD(T)] level of theory. Four hybrid functionals,B3LYP, M06-2X, TPSSh, and PBE0, were also employed in the calculations for the sake of comparison. In comparison ofthe CCSD(T) results, B3LYP, TPSSh, and PBE0 functionals can obtain more appropriate results than M06-2X and MP2.The analyses on molecular orbitals show that the 7s, 6d, and 5f atomic orbitals of actinide (An) atoms participate in thebonding of An–O bonds. The partial covalent nature between An and O atoms is revealed by QTAIM analyses.

Minimum-Modified Debye-Hückel Theory for Size-Asymmetric Electrolyte Solutions with Moderate Concentrations

A minimum-modified Debye-Hückel(DH)theory for electrolytes with size asymmetry is developed.Com-pared with the conventional DH theory,the minimum-modified DH theory only introduces an extra surface charge density to capture the electrostatic effect of the size asymmetry of the electrolytes and hence facilitates a boundary element method for electrostatic potential calculation.This theory can distinguish the electrostat-ic energies and excess chemical potentials of ions with the same sizes but opposite charges,and is applied to a binary primitive electrolyte solution with moderate electrostatic coupling.Compared with the hyper-netted chain theory,the validity of this modified DH theory demonstrates significant improvement over the conventional DH theory.

A theoretical study on the molecular structure and chemical reactivity of traditional Chinese medicine extract isopimpinellin

Isopimpinellin(C13H10O5),alternative name 5,8-dimethoxypsoralen,is one of the furocoumarin compounds.This traditional Chinese medicine extract has attracted a great deal of attention in recent years due to its pharmacological properties,especially its antifungal effect.The main purpose of this study was to study the molecular structure and chemical reactivity of isopimpinellin using the density functional theory method.To understand and interpret the reactivity of isopimpinellin,various chemical reactivity descriptors such as chemical potential(μ),electronegativity(χ),chemical hardness(η)and electrophilicity(ω)and local reactivity index condensed Fukui function(fi(r))have been calculated with five hybrid functionals PBE1PBE,MPW1PW91,B3LYP,X3LYP and B3PW91.These chemical reactivity descriptors indicate that the isopimpinellin molecule has a good antioxidant activity,which could be one of the reasons for its action as an effective antifungal drug.The condensed Fukui functions of isopimpinellin molecule provide a complete scheme of chemical reactivity of one molecule.

Shear Viscosity of Hot QED at Finite Chemical Potential from Kubo Formula

Within the framework of finite temperature field theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient.The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively.

Ab Initio Prediction of ^(29)Si-NMR Chemical Shifts

The ability of several ab initio models to predict experimental 29Si-NMR chemical shift is examined. The shielding values of trimethylsilyl chloride (A), t-butyldimethylsilyl chloride (B) and allyltrimethylsilane (C) are calculated by GIAO , CSGT and IGAIM methods, using HF/6-31G*, B3LYP/6-31G*, HF/6-311+G **, B3LYP/6-311+G ** and MPW1PW91/6-311+G ** models respectively. The 29Si chemical shifts calculated by GIAO method using HF/6-311+G ** model are highly in agreement with those obtained experimentally. All of the models above reproduce the trends of chemical shifts in all cases studied, suggesting that the models are of practical value.

盐溶液饱和岩土的本构理论及在黏土中的应用

盐溶液中离子的化学活性会改变饱和岩土的力学性质,诱发其工程性能出现劣化甚至失效等岩土工程问题。为了研究化学活性对饱和岩土水力与变形特性的影响,基于混合物理论与热力学溶液理论,建立了盐溶液饱和岩土材料的本构理论框架。与以往研究不同,该理论将固相应变分解为孔隙率变化引起的骨架应变、固相材料变形引起的基质应变以及化学反应等物质交换引起的质量交换应变,用以凸显孔隙率在水-力-化学多场耦合机制中的关键作用;采用溶质的现时质量分数作为化学状态变量来反映化学活性的影响;利用自由能和耗散势分别建立弹性和塑性本构关系。根据该理论框架建立了NaCl溶液饱和黏土的固相、流相本构关系以及溶质的渗流-扩散方程,并得到了已有试验数据的验证,表明该框架可以指导盐溶液饱和岩土的本构建模工作。