The coordination engineering of catalytic centers emerges as a pivotal strategy for precise electronic configuration modulation in photocatalytic CO_(2) reduction.Herein,the electronic structure of active sites in pol...The coordination engineering of catalytic centers emerges as a pivotal strategy for precise electronic configuration modulation in photocatalytic CO_(2) reduction.Herein,the electronic structure of active sites in polypyridine nickel catalysts is well modified through strategic ligand variation(bipyridine,terpyridine(TPY),2,6-di(1-pyrazolyl)pyridine)and anion coordination(NO_(3)^(-),Cl^(-),and CH_(3)COO^(-)),achieving enhanced CO_(2) performance.Crucially,covalent immobilization of these molecular catalysts within the COF-OH framework not only preserves their precisely defined and structurally adaptable characteristics but also demonstrates synergistic enhancement of CO_(2) adsorption capacity and charge transfer kinetics,as verified by CO_(2) adsorption isothermal analysis and ultrafast time-resolved transient absorption spectroscopy.Remarkably,COF-O-TPYNi(NO_(3)^(-))catalyst exhibits a CO_(2)-to-CO reduction activity of 9006.0μmol·g^(-1)·h^(-1)with 95.9%selectivity,superior to its counterpart catalysts,directly validating the mechanistic significance of precisely tailored coordination microenvironments around Ni active sites.Mechanistic studies through in situ XAFS,in situ ATR-SEIRAS and theoretical calculations reveal that this performance improvement over COF-O-TPYNi(NO_(3)^(-))is attributed to the reduced reaction energy barrier of*COOH generation.This work pioneers a coordination shell engineering paradigm for rational design of molecularly defined catalytic architectures.展开更多
Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially...Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz-Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.展开更多
The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron sp...The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron spectroscopy （XPS）. At 105 K, HCOOH molecularly adsorbs on clean Au（997） and interacts more strongly with low‐coordinated Au atoms at （111） step sites than with those at （111） terrace sites. On an atomic oxygen‐covered Au（997） surface, HCOOH reacts with oxygen at‐oms to form HCOO and OH at 105 K. Upon subsequent heating, surface reactions occur among ad‐sorbed HCOO, OH, and atomic oxygen and produce CO2, H2O, and HCOOH between 250 and 400 K. The Au（111） steps bind surface adsorbates more strongly than the Au（111） terraces and exhibit larger barriers for HCOO（a） oxidation reactions. The surface reactions also depend on the relative coverages of co‐existing surface species. Our results elucidate the elementary surface reactions between formic acid and oxygen adatoms on Au surfaces and highlight the effects of the coordina‐tion number of the Au atoms on the Au catalysis.展开更多
Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechan...Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory.It is found that the Volmer step is the ratelimiting step of HER on the Zn(002)and(100)surfaces,while,the reaction rates of HER on the Zn(101),(102)and(103)surfaces are determined by the Tafel step.Moreover,the correlation between HER activity and the generalized coordination number(CN)of Zn at the surfaces has been revealed.The relatively weaker HER activity on Zn(002)surface can be attributed to the higher CN of surface Zn atom.The atomically uneven Zn(002)surface shows significantly higher HER activity than the flat Zn(002)surface as the CN of the surface Zn atom is lowered.The CN of surface Zn atom is proposed as a key descriptor of HER activity.Tuning the CN of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies.Furthermore,this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface.展开更多
The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s...The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.展开更多
We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties....We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.展开更多
Crushing characteristics of single particles are the basis of granular material simulation with discrete element method(DEM).To improve the universality and precision of crushable DEM model,inhomogeneous stiffness and...Crushing characteristics of single particles are the basis of granular material simulation with discrete element method(DEM).To improve the universality and precision of crushable DEM model,inhomogeneous stiffness and strength properties are introduced into the bonded particle method,with which the Weibull distribution and size effect of particle strength can be reproduced without deleting elementary balls.The issues of particle strength and carrying capacity under complex contact conditions are investigated in this work by symmetric loading tests,asymmetric loading tests,and ball-ball loading tests.Results of numerical experiments indicate that particle carrying capacity is significantly influenced by coordination numbers,the symmetry of contact points,as well as the relative size of its neighbors.Contact conditions also show impact on single-particle crushing categories and the origin position of inner particle cracks.The existing stress indexes and assumptions of particle crushing criterion are proved to be inappropriate for general loading cases.Both the inherent inhomogeneity and contact conditions of particles should be taken into consideration in the simulation of granular materials.展开更多
The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,whi...The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.展开更多
According to the simulation of nitrogen sorption process in porous media with three-dimensional network model, and the analysis for such a process with percolation theory, a new method is proposed to determine a pore ...According to the simulation of nitrogen sorption process in porous media with three-dimensional network model, and the analysis for such a process with percolation theory, a new method is proposed to determine a pore structure parameter--mean coordination number of pore network, which represents the connectivity among a great number of pores. Here the 'chamber-throat' model and the Weibull distribution are used to describe the pore geometry and the pore size distribution respectively. This method is based on the scaling law of percolation theory after both effects of sorption thermodynamics and pore size on the sorption hysteresis loops are considered. The results show that it is an effective procedure to calculate the mean coordination number for micro- and meso-porous media.展开更多
Random packings of spherical particles have attracted attention for many years.An algorithm based on compression is developed to generate random packings of spherical particles in this paper.This method is different f...Random packings of spherical particles have attracted attention for many years.An algorithm based on compression is developed to generate random packings of spherical particles in this paper.This method is different from previous compression-based algorithm.In order to increase the packing density,a process of shaking is applied during packing process.The algorithm is mainly composed of three procedures:generating initial packing configuration by using random sequential adsorption(RSA),compressing packing domain,and shaking.The packing structure is characterized by packing density and coordinate number.The packing density increases with iteration number and a stable packing configuration is obtained after the iteration number is more than 34 000.The packing density is 0.85 and the average coordinate number is 3.7 in a stable packing configuration.展开更多
The distribution of Al （j） and the structural units distribution of Qi T in calcium aluminosilicate melts were studied by means of molecular dynamics simulation. The results show that provided there exists lower-fie...The distribution of Al （j） and the structural units distribution of Qi T in calcium aluminosilicate melts were studied by means of molecular dynamics simulation. The results show that provided there exists lower-field strength cation relative to Al3+, such as alkaline and alkaline earth metals, Al will be four-coordinated but not six-coordinated. Meanwhile, if there exist a large number of higher-field strength cations such as Si4+ and little lower-field strength cation, six-coordinated aluminum will be formed. The relation of structural units distribution of Qi T with chemical composition shift was also extracted, showing that as Ca2+ exists, the distributions of Qi Si, Qi Al or Qi T have the similar changing trend with the variation of component. Because of high-temperature effect, the Al-tetrahedral units in melts are greatly active and unstable and there exist dynamic transforming equilibria of Al（3）Al（4） and （Al（5））Al（4）. The three-coordinated oxygen and charge-compensated bridging oxygen are proposed to explain phenomena of the negative charge redundancy of AlO4 and location of network modifier with charge-compensated function in aluminosilicate melts.展开更多
The thermodynamics and the phase diagram of random field Ising model （RFIM） on Bethe lattice are studied by using a replica trick. This lattice is placed in an external magnetic field （B）. A Gaussian distribution ...The thermodynamics and the phase diagram of random field Ising model （RFIM） on Bethe lattice are studied by using a replica trick. This lattice is placed in an external magnetic field （B）. A Gaussian distribution of random field （hi） with zero mean and variance （hi2 = H2RF is considered. The free-energy （F）, the magnetization （M） and the order parameter （q） are investigated for several values of coordination number （z）. The phase diagram shows several interesting behaviours and presents tricritical point at critical temperature Tc = J/k and when HRF = 0 for finite z. The free-energy （F） values increase as T increases for different intensities of random field （HRE） and finite z. The internal energy （U） has a similar behaviour to that obtained from the Monte Carlo simulations. The ground state of magnetization decreases as the intensity of random field HRF increases, The ferromagnetic （FM） paramagnetic （PM） phase boundary is clearly observed only when z →∞. While FM PM-spin glass （SG） phase boundaries are present for finite z. The magnetic susceptibility （X） shows a sharp cusp at Tc in a small random field for finite z and rounded different peaks on increasing HRF.展开更多
Simulations of undrained tests were performed in a periodic cell using three dimensional(3D) discrete element method(DEM) program TRUBAL.The effective undrained stress paths are shown to be qualitatively similar to pu...Simulations of undrained tests were performed in a periodic cell using three dimensional(3D) discrete element method(DEM) program TRUBAL.The effective undrained stress paths are shown to be qualitatively similar to published physical experimental results of cohesionless media such as sand.Liquefaction and temporary liquefaction are observed for very loose samples and medium loose samples,respectively.A new micromechanical parameter is proposed to identify whether liquefaction or temporary liquefaction occurs in terms of a redundancy factor.The relationship of redundancy factor and average coordination number is derived theoretically.It is demonstrated that the phase transition dividing the solid-like behaviour and liquid-like behaviour is associated with a redundancy factor of 1,which corresponds to an average coordination number slightly above 4.展开更多
Some basic characteristics of lanthanide-oxygen bonds in various trivalent lanthanide metal-organic complexes are quantitatively studied by the bond valence model. Some important relationships among the electronegativ...Some basic characteristics of lanthanide-oxygen bonds in various trivalent lanthanide metal-organic complexes are quantitatively studied by the bond valence model. Some important relationships among the electronegativity, bond valence parameter, bond length and lanthanide coordination number in these complexes are generally found , which show that for each trivalent lanthanide cation all calculated parameters may well be correlated with its coordination number in their coordination complexes. Specifically,32 new data for the bond valence parameter are first calculated in this work.An approximate linear relationship between the Ln-O bond valence parameter and the coordination number of Ln^(3+) is obtained.The Ln-O bond length increases with the increase in the lanthanide coordination number.The difference of electronegative values decreases with the increase in the lanthanide coordination number.展开更多
The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed....The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed.The coordination numbers of Eu^(2+)in both NaBF_4 and Na_2SiF_6 hosts are less than 8.展开更多
Molecular dynamics simulation was used to study the interaction between anions,cations and water molecules in the brine of Laguocuo salt lake in Tibet.Taking the four stages of particle concentration changes during th...Molecular dynamics simulation was used to study the interaction between anions,cations and water molecules in the brine of Laguocuo salt lake in Tibet.Taking the four stages of particle concentration changes during the isothermal evaporation of salt lake brine as the research objects,the diffusion coefficient,coordination number,mean square displacement and radial distribution function of different systems were calculated respectively.The calculation results show that when the liquid concentration was lower,the H_(2)O molecule had an inhibitory effect on the interaction between the ions,when the ion concentration in the liquid phase was higher,SO_(4)2-competed easily with CO 32-for Li^(+)to form an ion pair,thus affecting the enrichment of Li^(+)in salt lake brine.The results of this paper provide a mechanism explanation for the migration behavior of Li^(+)in salt lake brine,it has laid a theoretical foundation for the development of lithium extraction from salt lake brine.展开更多
The reaction of[CpMo(CO)3]2 with dicyclopentamethylenethiuram disulfide in refluxing xylene resulted a novel mono nuclear complex,cis-[(CpMo(CO)2{S2C-N(CH2)5}]as red crystals in moderate yield.The compound was formed ...The reaction of[CpMo(CO)3]2 with dicyclopentamethylenethiuram disulfide in refluxing xylene resulted a novel mono nuclear complex,cis-[(CpMo(CO)2{S2C-N(CH2)5}]as red crystals in moderate yield.The compound was formed by the oxidative cleavage of metal-metal bond in[CpMo(CO)3]2 together with a reductive sulfur-sulfur bond scission in the ligand.展开更多
In the field of nano energy,investigating the specific heat capacity and coordination number of nano-confined water is highly significant for gaining a better understanding of the energy and microstructure of confined...In the field of nano energy,investigating the specific heat capacity and coordination number of nano-confined water is highly significant for gaining a better understanding of the energy and microstructure of confined water.In this work,we employed the method of molecular dynamics(MD)simulation to calculate the specific heat capacity at constant volume and coordination number of water molecules confined in carbon nanotubes(CNTs)under different conditions(T=600-700 K,P=21.776 and 25 MPa,CNT diameter=0.949-5.017nm).The results showed that near the critical point,the specific heat capacity at constant volume of confined water was lower than that of bulk water,and the energy fluctuation showed a trend of first increasing and then remaining unchanged with the increase of temperature and CNT diameter.Among them,the saturation point of temperature is 650 K(reduced pressure P_(r)=1)and 660 K(P_(r)=1.15),and the saturation point of CNT diameter is 2.034 nm.Additionally,the pseudo-critical temperature of confined water was the same as bulk water,and it increased with the increase of critical pressure.Moreover,with the increase of CNT diameter,the coordination number of confined water increased rapidly,and reaches the saturation state when the CNT diameter is 2.034 nm.This investigation revealed the mass and energy characteristics of nano-confined water near the critical point,which could provide guidance for the critical phase transition of nano-confined water.展开更多
The novel ytterbium coordination polymer is a two dimensional framework in which the central metal ions have four different coordination numbers and form four kinds of coordination polyhedra. The four kinds of coordi...The novel ytterbium coordination polymer is a two dimensional framework in which the central metal ions have four different coordination numbers and form four kinds of coordination polyhedra. The four kinds of coordination polyhedra connect into infinite chains by sharing oxygen atoms展开更多
In granulation, fine particles combine to form a coarse granule in the form of a particle matrix partially or fully saturated with a binder liquid. The final product of granulation possesses a wide variety of granule ...In granulation, fine particles combine to form a coarse granule in the form of a particle matrix partially or fully saturated with a binder liquid. The final product of granulation possesses a wide variety of granule size distributions with surface mean diameters which differ with operating conditions. The final granule size depends on the operating conditions, e.g. operating gas velocity, inlet air temperature, initial feed particle size, and viscosity of the binder. The objective of this paper is to find out the uniformity in the relation between the granule mass fraction in the final granule size distribution and the number of feed particles present in the granules. The total number of granules obtained depends on the experimental conditions but the granule mass fraction and the number of feed particles forming a single granule are independent of operating variables, feed material and method of granulation. The paper purports further to compare the uniform nature of mass fraction of the granules in final granule size distribution and the primary particles required to form that particular granule size irrespective of experimental conditions of granulation.展开更多
文摘The coordination engineering of catalytic centers emerges as a pivotal strategy for precise electronic configuration modulation in photocatalytic CO_(2) reduction.Herein,the electronic structure of active sites in polypyridine nickel catalysts is well modified through strategic ligand variation(bipyridine,terpyridine(TPY),2,6-di(1-pyrazolyl)pyridine)and anion coordination(NO_(3)^(-),Cl^(-),and CH_(3)COO^(-)),achieving enhanced CO_(2) performance.Crucially,covalent immobilization of these molecular catalysts within the COF-OH framework not only preserves their precisely defined and structurally adaptable characteristics but also demonstrates synergistic enhancement of CO_(2) adsorption capacity and charge transfer kinetics,as verified by CO_(2) adsorption isothermal analysis and ultrafast time-resolved transient absorption spectroscopy.Remarkably,COF-O-TPYNi(NO_(3)^(-))catalyst exhibits a CO_(2)-to-CO reduction activity of 9006.0μmol·g^(-1)·h^(-1)with 95.9%selectivity,superior to its counterpart catalysts,directly validating the mechanistic significance of precisely tailored coordination microenvironments around Ni active sites.Mechanistic studies through in situ XAFS,in situ ATR-SEIRAS and theoretical calculations reveal that this performance improvement over COF-O-TPYNi(NO_(3)^(-))is attributed to the reduced reaction energy barrier of*COOH generation.This work pioneers a coordination shell engineering paradigm for rational design of molecularly defined catalytic architectures.
基金supported by the National High Techology Research and Development Program(No.2012AA050103)
文摘Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz-Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.
基金supported by the National Basic Research Program of China (973 Program, 2013CB933104)the National Natural Science Foundation of China (21525313, 20973161, 21373192)+1 种基金the Fundamental Research Funds for the Central Universities (WK2060030017)Collaborative In-novation Center of Suzhou Nano Science and Technology~~
文摘The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron spectroscopy （XPS）. At 105 K, HCOOH molecularly adsorbs on clean Au（997） and interacts more strongly with low‐coordinated Au atoms at （111） step sites than with those at （111） terrace sites. On an atomic oxygen‐covered Au（997） surface, HCOOH reacts with oxygen at‐oms to form HCOO and OH at 105 K. Upon subsequent heating, surface reactions occur among ad‐sorbed HCOO, OH, and atomic oxygen and produce CO2, H2O, and HCOOH between 250 and 400 K. The Au（111） steps bind surface adsorbates more strongly than the Au（111） terraces and exhibit larger barriers for HCOO（a） oxidation reactions. The surface reactions also depend on the relative coverages of co‐existing surface species. Our results elucidate the elementary surface reactions between formic acid and oxygen adatoms on Au surfaces and highlight the effects of the coordina‐tion number of the Au atoms on the Au catalysis.
基金This work was financially supported by the National Natural Science Foundation of China(22075171)Natural Science Foundation of Shanghai(23ZR1423400)The firstprinciples calculations were supported by the High Performance Computing Center of Shanghai University.
文摘Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory.It is found that the Volmer step is the ratelimiting step of HER on the Zn(002)and(100)surfaces,while,the reaction rates of HER on the Zn(101),(102)and(103)surfaces are determined by the Tafel step.Moreover,the correlation between HER activity and the generalized coordination number(CN)of Zn at the surfaces has been revealed.The relatively weaker HER activity on Zn(002)surface can be attributed to the higher CN of surface Zn atom.The atomically uneven Zn(002)surface shows significantly higher HER activity than the flat Zn(002)surface as the CN of the surface Zn atom is lowered.The CN of surface Zn atom is proposed as a key descriptor of HER activity.Tuning the CN of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies.Furthermore,this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface.
基金supported by the National Natural Science Foundation of China(51125009,91434118,21401185,21521092)Hundred Talents Program of Chinese Academy of SciencesJilin Province Science and Technology Development Project(20170101092JC,20160520006JH)
文摘The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.
文摘We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.
基金the National Natural Science Foundation of China(No.11772117)for financial support.
文摘Crushing characteristics of single particles are the basis of granular material simulation with discrete element method(DEM).To improve the universality and precision of crushable DEM model,inhomogeneous stiffness and strength properties are introduced into the bonded particle method,with which the Weibull distribution and size effect of particle strength can be reproduced without deleting elementary balls.The issues of particle strength and carrying capacity under complex contact conditions are investigated in this work by symmetric loading tests,asymmetric loading tests,and ball-ball loading tests.Results of numerical experiments indicate that particle carrying capacity is significantly influenced by coordination numbers,the symmetry of contact points,as well as the relative size of its neighbors.Contact conditions also show impact on single-particle crushing categories and the origin position of inner particle cracks.The existing stress indexes and assumptions of particle crushing criterion are proved to be inappropriate for general loading cases.Both the inherent inhomogeneity and contact conditions of particles should be taken into consideration in the simulation of granular materials.
基金funded by the National Key Research and Development Program of China(2017YFA0700103,2018YFA0704502)the National Natural Science Foundation of China(21703248)staffs in BL11B beamline in Shanghai Synchrotron Radiation Facility(SSRF)for their technical assistance(2020-SSRF-PT-012223 and 2021-SSRF-PT-015319)。
文摘The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.
基金Supported by the National Natural Science Foundation of China(No.29776038).
文摘According to the simulation of nitrogen sorption process in porous media with three-dimensional network model, and the analysis for such a process with percolation theory, a new method is proposed to determine a pore structure parameter--mean coordination number of pore network, which represents the connectivity among a great number of pores. Here the 'chamber-throat' model and the Weibull distribution are used to describe the pore geometry and the pore size distribution respectively. This method is based on the scaling law of percolation theory after both effects of sorption thermodynamics and pore size on the sorption hysteresis loops are considered. The results show that it is an effective procedure to calculate the mean coordination number for micro- and meso-porous media.
基金National Key Basic Research and Developing Project,China(973 program) (No. 2005CB623902)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Random packings of spherical particles have attracted attention for many years.An algorithm based on compression is developed to generate random packings of spherical particles in this paper.This method is different from previous compression-based algorithm.In order to increase the packing density,a process of shaking is applied during packing process.The algorithm is mainly composed of three procedures:generating initial packing configuration by using random sequential adsorption(RSA),compressing packing domain,and shaking.The packing structure is characterized by packing density and coordinate number.The packing density increases with iteration number and a stable packing configuration is obtained after the iteration number is more than 34 000.The packing density is 0.85 and the average coordinate number is 3.7 in a stable packing configuration.
文摘The distribution of Al （j） and the structural units distribution of Qi T in calcium aluminosilicate melts were studied by means of molecular dynamics simulation. The results show that provided there exists lower-field strength cation relative to Al3+, such as alkaline and alkaline earth metals, Al will be four-coordinated but not six-coordinated. Meanwhile, if there exist a large number of higher-field strength cations such as Si4+ and little lower-field strength cation, six-coordinated aluminum will be formed. The relation of structural units distribution of Qi T with chemical composition shift was also extracted, showing that as Ca2+ exists, the distributions of Qi Si, Qi Al or Qi T have the similar changing trend with the variation of component. Because of high-temperature effect, the Al-tetrahedral units in melts are greatly active and unstable and there exist dynamic transforming equilibria of Al（3）Al（4） and （Al（5））Al（4）. The three-coordinated oxygen and charge-compensated bridging oxygen are proposed to explain phenomena of the negative charge redundancy of AlO4 and location of network modifier with charge-compensated function in aluminosilicate melts.
文摘The thermodynamics and the phase diagram of random field Ising model （RFIM） on Bethe lattice are studied by using a replica trick. This lattice is placed in an external magnetic field （B）. A Gaussian distribution of random field （hi） with zero mean and variance （hi2 = H2RF is considered. The free-energy （F）, the magnetization （M） and the order parameter （q） are investigated for several values of coordination number （z）. The phase diagram shows several interesting behaviours and presents tricritical point at critical temperature Tc = J/k and when HRF = 0 for finite z. The free-energy （F） values increase as T increases for different intensities of random field （HRE） and finite z. The internal energy （U） has a similar behaviour to that obtained from the Monte Carlo simulations. The ground state of magnetization decreases as the intensity of random field HRF increases, The ferromagnetic （FM） paramagnetic （PM） phase boundary is clearly observed only when z →∞. While FM PM-spin glass （SG） phase boundaries are present for finite z. The magnetic susceptibility （X） shows a sharp cusp at Tc in a small random field for finite z and rounded different peaks on increasing HRF.
基金Project(GR/R91588) supported by the Engineering and Physical Sciences Research Council,UK
文摘Simulations of undrained tests were performed in a periodic cell using three dimensional(3D) discrete element method(DEM) program TRUBAL.The effective undrained stress paths are shown to be qualitatively similar to published physical experimental results of cohesionless media such as sand.Liquefaction and temporary liquefaction are observed for very loose samples and medium loose samples,respectively.A new micromechanical parameter is proposed to identify whether liquefaction or temporary liquefaction occurs in terms of a redundancy factor.The relationship of redundancy factor and average coordination number is derived theoretically.It is demonstrated that the phase transition dividing the solid-like behaviour and liquid-like behaviour is associated with a redundancy factor of 1,which corresponds to an average coordination number slightly above 4.
文摘Some basic characteristics of lanthanide-oxygen bonds in various trivalent lanthanide metal-organic complexes are quantitatively studied by the bond valence model. Some important relationships among the electronegativity, bond valence parameter, bond length and lanthanide coordination number in these complexes are generally found , which show that for each trivalent lanthanide cation all calculated parameters may well be correlated with its coordination number in their coordination complexes. Specifically,32 new data for the bond valence parameter are first calculated in this work.An approximate linear relationship between the Ln-O bond valence parameter and the coordination number of Ln^(3+) is obtained.The Ln-O bond length increases with the increase in the lanthanide coordination number.The difference of electronegative values decreases with the increase in the lanthanide coordination number.
基金Project supported by the National Natural Science Foundation of China.
文摘The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed.The coordination numbers of Eu^(2+)in both NaBF_4 and Na_2SiF_6 hosts are less than 8.
基金the CAS of STS(grant numbers KFJ-STS-QYZD-2021-06-002)Innovation Academy for Green Manufacture,Chinese Academy of Sciences(grant number IAGM2020C01).
文摘Molecular dynamics simulation was used to study the interaction between anions,cations and water molecules in the brine of Laguocuo salt lake in Tibet.Taking the four stages of particle concentration changes during the isothermal evaporation of salt lake brine as the research objects,the diffusion coefficient,coordination number,mean square displacement and radial distribution function of different systems were calculated respectively.The calculation results show that when the liquid concentration was lower,the H_(2)O molecule had an inhibitory effect on the interaction between the ions,when the ion concentration in the liquid phase was higher,SO_(4)2-competed easily with CO 32-for Li^(+)to form an ion pair,thus affecting the enrichment of Li^(+)in salt lake brine.The results of this paper provide a mechanism explanation for the migration behavior of Li^(+)in salt lake brine,it has laid a theoretical foundation for the development of lithium extraction from salt lake brine.
文摘The reaction of[CpMo(CO)3]2 with dicyclopentamethylenethiuram disulfide in refluxing xylene resulted a novel mono nuclear complex,cis-[(CpMo(CO)2{S2C-N(CH2)5}]as red crystals in moderate yield.The compound was formed by the oxidative cleavage of metal-metal bond in[CpMo(CO)3]2 together with a reductive sulfur-sulfur bond scission in the ligand.
基金financially supported by the National Key R&D Program of China(2020YFA0714400)the Fundamental Research Funds for the Central Universities(xzy022023036)。
文摘In the field of nano energy,investigating the specific heat capacity and coordination number of nano-confined water is highly significant for gaining a better understanding of the energy and microstructure of confined water.In this work,we employed the method of molecular dynamics(MD)simulation to calculate the specific heat capacity at constant volume and coordination number of water molecules confined in carbon nanotubes(CNTs)under different conditions(T=600-700 K,P=21.776 and 25 MPa,CNT diameter=0.949-5.017nm).The results showed that near the critical point,the specific heat capacity at constant volume of confined water was lower than that of bulk water,and the energy fluctuation showed a trend of first increasing and then remaining unchanged with the increase of temperature and CNT diameter.Among them,the saturation point of temperature is 650 K(reduced pressure P_(r)=1)and 660 K(P_(r)=1.15),and the saturation point of CNT diameter is 2.034 nm.Additionally,the pseudo-critical temperature of confined water was the same as bulk water,and it increased with the increase of critical pressure.Moreover,with the increase of CNT diameter,the coordination number of confined water increased rapidly,and reaches the saturation state when the CNT diameter is 2.034 nm.This investigation revealed the mass and energy characteristics of nano-confined water near the critical point,which could provide guidance for the critical phase transition of nano-confined water.
文摘The novel ytterbium coordination polymer is a two dimensional framework in which the central metal ions have four different coordination numbers and form four kinds of coordination polyhedra. The four kinds of coordination polyhedra connect into infinite chains by sharing oxygen atoms
文摘In granulation, fine particles combine to form a coarse granule in the form of a particle matrix partially or fully saturated with a binder liquid. The final product of granulation possesses a wide variety of granule size distributions with surface mean diameters which differ with operating conditions. The final granule size depends on the operating conditions, e.g. operating gas velocity, inlet air temperature, initial feed particle size, and viscosity of the binder. The objective of this paper is to find out the uniformity in the relation between the granule mass fraction in the final granule size distribution and the number of feed particles present in the granules. The total number of granules obtained depends on the experimental conditions but the granule mass fraction and the number of feed particles forming a single granule are independent of operating variables, feed material and method of granulation. The paper purports further to compare the uniform nature of mass fraction of the granules in final granule size distribution and the primary particles required to form that particular granule size irrespective of experimental conditions of granulation.
