Fractal phenomena in molecular mechanics calculation

It is proposed that in molecular mechanics calculation points belonging to various stable or meta-sta-ble conformtrs are mixed up and form fractal structures in conformation space.The calculation results show the following two phenomena:(i)Two levels of structure with fractal feature were observed.Around the conformer without mirror symmetry points belonging to the conformer and its enantiomer are mixed up and form the first level of fractal structure; on the boundary of the attractive basin o{ each atlractor,points belonging to different attractors form the second level of fractal structure.(ii) The variation of molecular mechanics parameters will influence the structure and area of each attractive basin significantly The above phenomena may become the basis of a new method for solving the troublesome multi-minimum-point problem in molecular mechanics calculation.     

Temperature Controlled Lateral Pattern Formation in Confined Polymer Thin Films

The thermal induced topography change in a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been studied by using AFM. Regular lateral patterns over large areas were observed on the surface when the system was heated to a sufficiently high temperature. 2D-FFT analysis to the AFM images indicates that the patterns are isotropic and have well defined periodicities. The periodicities of the characteristic patterns are found to depend strongly on the annealing temperature. The study of the ki-netics of the formation reveals that such a topography forms almost instantaneously once the critical tempera-ture is reached. It is suggested that this wave-like surface morphology is driven by the thermal expansion co-efficient mismatch of the different layers. This method for generating regular wave-like patterns could be used as a general method for patterning various organic materials into micro/nanostructures.     

PROBABILITY CORRELATION OF ∑_1 RELATION-SHIPS AND THEIR TABLES OF 230 SPACE GROUPS

In the present paper, using the structure factor algebra method, we discuss the correla-tion and the distinction between thte conventionally used ∑_1 relationships and the probabilityvalue of P_ (h_1) on the basis of the P_ (h_1) of Hauptman's ana Karle's ∑_1 relationship. Theintroduction of conception on equivalent point weight ω of h_1 and degeneracy ω_2 of h_2 makesthe probability P_ (h_1) expressed by ∑_1 relationships become more strict. There are a lot ofinterrelated ∑_1 relationships in all four high symmetry crystal systems. According to theresults of this paper, what we need is noly to retain a few independent ∑_1 relationships. Usingthe principle of linearization, we have completed the tables of the ∑_1 relationships for 156space groups which belong to tetragonal, trigonal, hexagonal and cubic crystal systems.Now, we present the concise and perfect tables of 230 space groups of which 74 wereaccomplished by Hasek.     

Thermodynamic Foundation for High Temperature Electrochemistry

Thermodynamic concepts required for the thermodynamic calculation of the potentials of electrodes for high temperature applications are briefly reviewed. A thermodynamic approach to the calculation of half cell potentials and the standard chemical potential of an electron at high temperatures which are related to the Standard Hydrogen Electrode(SHE) is discussed. As examples, an external Ag/AgCl reference electrode and a YSZ(Ag|O2) pH sensor for high temperature applications are analyzed by using the thermodynamic ap-proach to derive a high temperature pH measurement equation. The two electrodes are employed to measure high temperature pH and the measured pH was compared with the calculated pH by using a solution chem-istry method. Concepts and principles for electrode kinetics are also briefly introduced and a modification to the Tafel equations is suggested.     

PHYLETIC RELATIONSHIP OF PROTEIN STRUCTURES BASED ON SPATIAL PREFERENCE OF RESIDUES

A distance measure that infers to indicate the evolutionary relationship of protein structures has been developed based on spatial preference factors of residues. The spatial preference factor is a reflection of the environment of residues in tertiary structure. Compared with the phyletic relationships derived from sequence homologies and three-dimensional structures, we find that the two lines of evolution are similar in general. This approach is applied to a group of glins here.     

Recent progress on discovery and properties prediction of energy materials:Simple machine learning meets complex quantum chemistry

In nature,the properties of matter are ultimately governed by the electronic structures.Quantum chemistry(QC)at electronic level matches well with a few simple physical assumptions in solving simple problems.To date,machine learning(ML)algorithm has been migrated to this field to simplify calculations and improve fidelity.This review introduces the basic information on universal electron structures of emerging energy materials and ML algorithms involved in the prediction of material properties.Then,the structure-property relationships based on ML algorithm and QC theory are reviewed.Especially,the summary of recently reported applications on classifying crystal structure,modeling electronic structure,optimizing experimental method,and predicting performance is provided.Last,an outlook on ML assisted QC calculation towards identifying emerging energy materials is also presented.     

Analytical derivative techniques for TDDFT excited-state properties: Theory and application

We review our recent work on the methodology development of the excited-state properties for the molecules in vacuum and liquid solution.The general algorithms of analytical energy derivatives for the specific properties such as the first and second geometrical derivatives and IR/Raman intensities are demonstrated in the framework of the time-dependent density functional theory(TDDFT).The performance of the analytical approaches on the calculation of excited-state energy Hessian has also been shown.It is found that the analytical approaches are superior to the finite-difference method on the computational accuracy and efficiency.The computational cost for a TDDFT excited-state Hessian calculation is only 2–3 times as that for the DFT ground-state Hessian calculation.With the low computational complexity of the developed analytical approaches,it becomes feasible to realize the large-scale numerical calculations on the excited-state vibrational frequencies,vibrational spectroscopies and the electronic-structure parameters which enter the spectrum calculations of electronic absorption and emission,and resonance Raman spectroscopies for medium-to large-sized systems.     

Effect of La_2O_3/γAl_2O_3 Catalyst on the Activation of CH_4 and CO_2 to C_02 Hydrocarbons under Non-equilibrium Plasma

The oxidative coupling of methane (OCM) to C2 hydrocarbons using carbon dioxide as oxidant is an attractive process from environmental point of view. Only a few research papers reported for it1-3. In general, the yield of C2 hydrocarbons was about 6%. This indicated that the method of catalytic activation was unfavorable to the reaction. It is necessary for us to find a new method in order to activate reaction and improve C2 hydrocarbon yield. Non-equilibrium plasma is a cold plasma in…     

NATURE OF THE A AND THE F MATRIX IN THE CALCULATION OF FORCE CONSTANTS OF MOLECULAR VIBRATION

In this paper,calculations of force constants of molecular vibrations are carried out by using Wilson GF matrix method.In the determination of force constants from frequencies and factorization of Gmatrix,an ordering relationship of A matrix(may be n dimensional) relative to L matrix was found according to the ordering of symmetry coordinates.With the help of inverse unitary transformation,a general method to calculate Ft from constants Fs was established.The additivity of Fr depending on the symmetry block was determined to be true.All the force constants in non-planar and planar of urea,thiourea and sclenouroa molecules were calculated by using the general va-leine force field.The calculated values of frequencies were com-pairec with other data given in the literature,and it was shown that the present calculation is in good agreement with the experimental     

A generalized mathematical model for non-catalytic gas-solid reactions

Based on a general classification and characteristic comparison of the existing models, a new model for non-catalytic gas-solid reactions is proposed and a general formulation for the model in terms of the solid conversion, X, is presented in this paper. The model, referred to the generalized model, is demonstrated to be applicable to any solid reactant of general structure ranging from highly porous to nonporous materials. It is shown that the generalized model incorporates the grain and pore structure for a solid pellet and can be reduced to the grain and random pore models as extreme cases.     

Recent Progress of Atmospheric Water Harvesting Using Metal-Organic Frameworks

Atmospheric water harvesting based on vapor adsorption is a newly emerged and potential technology to supply portable water for arid areas.To efficiently harvest vapor from the air,sorbents are required to have conside-rable adsorption capacity,easy regeneration and high stability.With the advantages of porous structure,tunable pore size and tailorable hydrophilicity,metal-organic frameworks(MOFs)have demonstrated excellent performance in vapor adsorption and water generation.In this review,we first discuss the degradation mechanisms of MOFs exposed to water and summarize the structure-stability relationship;by centering on the adsorption isotherms,the connection between the structure of MOFs and the water adsorption property is illuminated;finally,some prospects are suggested in order to push forward the progress of this technology.     

Rational design of porous carbon allotropes as anchoring materials for lithium sulfur batteries

The shuttle effect seriously impedes the development and practical application of lithium sulfur(Li-S)batteries.It is still a long-term challenge to find effective anchoring materials to hinder the shuttle effect of Li-S batteries.Using carbon allotrope as anchoring materials is an effective strategy to alleviate the shuttling effect.However,the influence factors of carbon allotrope on the adsorption performance of LIPSS at the atomic level are not clear,which limits the application of carbon allotrope in Li-S batteries.Herein,using first-principles simulations,a systematical calculation of carbon allotropes with various ring size(6 ≤S≤16) and shape is conducted to understand the adsorption mechanism.The results show that the T-G monolayers with suitable ring structure and high charge transfer can significantly enhance the interaction between the monolayer and LiPSs,allowing them to have high capacity and high coulombic efficiency.Further diffusion studies show that LiPSs on the T-G monolayer have the low diffusion barriers,which ensures the charging and discharging rate of batteries.Our studies could provide material design principles of carbon allotrope monolayers used as anchoring materials of the high performance Li-S batteries.     

The Harmonious Dissipative Operators and the Completely Square Conservative Difference Scheme in an Explicit Way

In this paper, a new definition on harmonious dissipative operators is given and some important properties of theirs are shown. Especially, the relationship between a harmonious dissipative operator and the completely square conservative difference scheme in an explicit way is revealed. Kinds of 2-order, 3-order and 4-order harmonious dissipative operators are constructed by using the traditional Runge-Kutta method and a species of general m-order harmonious dissipative operators is established in the linear case. In addition, an efficiency parameter to appraise the time benefits of a harmonious dissipative operator is defined in this paper. It is testified in numerical tests that the harmonious dissipative operators are indeed able to improve the time-efficiency and computational effect of the completely square conservative difference scheme in an explicit way.     

THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF POLYMERS WITH PHYSICAL CROSSLINKS*

The shape memory effect of polymers was investigated for the purpose of improving the processingconditions of their preparation and broadening the list of polymers for shape memory applications. Emphasiswas put on the possibility of using polymers with physical crosslinks as shape memory materials and theirstructure-function relationships. Segmented block polyurethanes and polyethylene/nylon 6 graft copolymerswere used as examples of polymers with physical crosslinks. It was found that these copolymers can really beused as thermally stimulated shape memory materials with large recoverable strain and high final recoveryrate. The main advantage of using copolymers is their improved processing conditions as compared withpolymers with chemical crosslinks. As only physical crosslinks are introduced, all conventional processingtechniques for thermal plastics can be used, and the materials become easily reusable. The results indicatethat the high crystallinity of these copolymers at room temperature and the formation of stable physicalcrosslinks are the two prerequisites for these polymers to exhibit shape memory effect. The successful use ofblock and graft copolymers imply the possibility of using polymers of various structure and properties asshape memory materials.     

非爆炸且不可还原农用硝酸铵的改性研究与测试技术

Based on a study of the relationship of ammonium nitrate （AN） explosion and its thermal stability, inert agents were added to AN for eliminating the explosive characteristic of AN and in order to be irrestorable. The results of using a large quantity of experiments and various testing technologies show that the improvement on thermal stability of modified AN is the basic reason for eliminating explosive characteristic of AN. The modification scheme was considered to have the following features： reliable and stable technology, market-demanded product, low investment and good economic returns. And during the revamping period, the normal production of AN will not be af- fected, and the economic, social and environmental benefits are good.     

Sequence Hiberarchy Evolution Measurement Method and its Application

A novel method based on discrete wavelet transform （DWT） and cross-covariance for revealing the evolution of species at different spatial resolutions is presented. The trypsin proteins of different species are chosen as an example to describe the evolution relationship according to the evolution vectors by using this method. The results indicated that this method is a promising approach to reveal species evolution at different spatial resolutions.     

Raising the capacity of lithium vanadium phosphate via anion and cation co-substitution

The pursuit for batteries with high specific energy provokes the research of high-voltage/capacity cathode materials with superior stability and safety as the alternative for lithium iron phosphate.Herein,using the sol-gel method,a lithium vanadium phosphate with higher average discharge voltage(3.8 V,vs.Li+/Li) was obtained from a single source for Mg2+ and Cl-co-substitution and uniform carbon coating,and a nearly theoretical capacity(130.1 mA h g^-1) and outstanding rate performance(25 C) are acquired together with splendid capacity retention(80%) after 650 cycles.This work reveals that the well-sized anion and cation substitution and uniform carbon coating are of both importance to accelerate kinetic performance in the context of nearly undisturbed crystal structure for other analogue materials.It is anticipated that the electrochemistry comprehension will shed light on preparing cathode materials with high energy density in the future.     

Adsorption of helical and saddle-shaped oligothiophenes on solid surface

The arrangement of oligothiophenes is essential for understanding the relationship between structure and properties particularly in the organic electronic field. The self-assembly behaviors of helical(TMS)2-[7]helicene(T1), naphthalene-cored double(TMS)2-[7]helicene(T2), and saddle-shaped cyclooctatetrathiophene(T3), its derivative α,α,α,α-tetraphenyl-cyclooctatetrathiophene(T4) on solid surface are firstly investigated by using a combination of scanning tunneling microscopy(STM) and density functional theory(DFT) calculation. 1,3,5-Tris(10-carboxydecyloxy)-benzene(TCDB) is selected to build flexible host networks to immobilize these oligothiophenes in order to capture their molecular adsorption images successfully. The observed monodisperse or polydisperse filling and long-range alignment of oligothiophenes are described based on the non-covalent interactions and commensurate structure between olihothiophene and cavity. We speculate that those molecularly defined alignments could lead to significantly understanding the application of such ordered monolayer in organic electronic devices.