2000 Vol. 13, No. 6

Article
The binary cluster of ammonia and methanol was studied using both laser MPI MS and the molecular beam technologies. Two serials of protonated cluster ions were measured:(CH3OH)n H+ and(CH3OH)n NH4+(1≤n≤14),which were produced from the proton transfer reactions in the binary clusters . The binary cluster of NH3 and CH3OD was also studied in the current work. The results showedthat the transfer probability of the D in OD was several times larger than that of the H in CH3 . The calculation of binary cluster of CH3OH - NH3 with HF / STO - 3G and MP2 / 6 - 31G** basis sets,showed that the proton in OH was easier to transfer than that in CH3,as there was a barrier about 120kJ / mol for the proton in CH3 to transfer.
The binary cluster of ammonia and methanol was studied using both laser MPI MS and the molecular beam technologies. Two serials of protonated cluster ions were measured:(CH3OH)n H+ and(CH3OH)n NH4+(1≤n≤14),which were produced from the proton transfer reactions in the binary clusters . The binary cluster of NH3 and CH3OD was also studied in the current work. The results showedthat the transfer probability of the D in OD was several times larger than that of the H in CH3 . The calculation of binary cluster of CH3OH - NH3 with HF / STO - 3G and MP2 / 6 - 31G** basis sets,showed that the proton in OH was easier to transfer than that in CH3,as there was a barrier about 120kJ / mol for the proton in CH3 to transfer.
Using a three - layer cluster model,we calculated the bonding energy of the Ag(110)- O(2× 1)phase by DFT method. O atoms are found to occupy the long - bridge site 0. 04_ above the silver atoms . At the same time,we confirmed the missing - row reconstruction with the formation of the - Ag -O - Ag - chains along the ‘ 110 a direction. The top three layers of Ag surface are strongly relabed,with an ebpansion of the first - to - second layer distance,and a contraction of the second - to - third incterlayer spacing,compared to the ideal silver crystal spacing,respectively. A pairing effect of the second-layer Ag atoms and a slightly buckling effect of the third - layer Ag atoms are also found. The results are well consistent with the ebperimental and other theoretical results.
Geometry optimization,the total energies and chemical shift of Si in H8Si8O12 and H8Si7TiO12clusters are calculated at the level of HF,MP2 and B3LYP employing 3 - 21G basis sets. The obtainedtheoretical results of geometry,together with the chimical shift of Si,H8Si8O12 cluster is in good agreementwith the experimental results. Geometry of H8Si7TiO12 cluster is also discussed.
Pressure - induced amorphization inα- quartz GeO2 has been investigated using constant -pressure molecular dynamics(MD)calculations with two - body potential. Interatomic potential functions of our new model are composed of Coulomb force,Short - range repulsion,van der Waals force,and Morse interactions. The calculations were carried out by an improved MD simulation program with a quantum correction(QC). Both the static properties and crystal - to - amorphous phase transition were very well reproduced. Through an analysis of the molar volume,angular correlation functions,pair correlation functions,change of the coordination number,we predict new structural transitions forα- quartz GeO2 when pressure over 6. 0GPa at room temperature,the new phase comprise mixed arrays of fourfold(33%)and sixfold(66%)Ge - O coordination.
By using the chemical bond theory of dielectric description,the Sn4 + ,I- Mossbauer isomershifts is studied. A linear relationship between the isomer shifts and the chemical surrounding factor h definedby the covalency of chemical bond fcμand the polarizabilitie of ligand bond volumeαLμis achieved:δ=δ0 + bh,h =(Σμ αLμfcμ)1 / 2 .
Intramolecular energy relaxation processes of rare earth complexes(RE(DBM)3,RE = Nd,Sm,Gd)have been studied by the photoacoustic amplitude and phase spectra. The amplitude intensities ofπ-π* transition of ligand in Sm(DBM)3,Gd(DBM)3 and Nd(DBM)3 increase gradually,but the phase data within the region of ligand absorption in the complexes of Gd,Sm and Nd decrease gradually,which shows intramolecular energy relaxation processes. For Gd(DBM)3 energy can’t transfer from the lowest triplet state of ligand to the 4f excited state of Gd3 + ,the triplet state relaxes to the ground state directly. For Sm(DBM)3 and Nd(DBM)3 energy can effectively transfer from the lowest triplet state of ligands to the 4f excited states of the central ions. The 4f excited states of Nd3 + almost relax nonradiatively to the ground state because the gap among the levels in Nd3 + is small. The energy of excited state in Sm3 + radiates partly because Sm3 + is a fluorescent ion. Combined these with the results of fluorescencespectra the models of intramolecular energy relaxation processes are established.
Polystrene(PS)-TiO2 nano-spheres were chemically synthesized. The structure characterization of theprepared PS-TiO2 nano-spheres was investigated by means of transmission electron microscopy(TEM)and Fouriertransform infrared spectroscopy(FTIR). The thermal stability of PS-TiO2 nano-spheres was identified using athermal analyzer(DSC & TGA). The tribological behaviors of PS-TiO2 nano-spheres as additives in paraffin oilwere evaluated on a four-ball machine. The worn surfaces were analyzed with X-ray photoelectron spectroscopy(XPS)also. Experimental results indicate that the PS-TiO2 nano-spheres,under a certain condition,have agood anti-wear performance and improve striking failure load. This is attributed to the formation of a chemical reactionboundary film consisting of TiO2,Fe2O3 and organic fragments.
The capacitance of nanoparticles is a very important parameter for the new kind of single -electron devices which are formed by nanoparticle quantum dot arry. Based on the few - body theory,thetheoretical model about quantum dot capacitance of nanoparticles are put forward. From this view,themaximum nanopariticle sizes,in which the room temperature single - electronics phenomena can still beobserved,have been forecasted. By means of harmonic potential model,the capacitance of semiconductornanoparticles CdS,PbS have been Simulated. The Simulation results show the maxinums of CdS,PbSnanoparticle sizes are 11 nm and 5 nm,respectively. The theoretical simulation results are in agreementwith experimentals.
Nanostructured(Y0.95Eu0.05)2O3 was synthesized through urea sol method,and n -(Y0.95Eu0.05)2O3 Particles / SiO2 aerogel assemblies were prepared by supercritical drying technique.The experimental results showed that we could achieve the maximum luminescence intensity by carefully choosing our optimal experimental conditions. When the molar ratio of Y3 + to Eu3 + equals 20:1,homogenous reaction for 4h,then under 680℃,4h annealing,the luminescence intensity of n -(Y0.95Eu0.05)2O3 was the maximum. In n -(Y0.95Eu0.05)2O3 / SiO2 aerogel assemblies,annealing under the same conditions,when the molar ratio of Si to 2Y equals 1: 7,the luminescence intensity of the assembly is the strongest,but it was still weaker than the luminescence intensity of n -(Y0.95Eu0.05)2O3 . And the phenomena of the luminescence intensity decrement of the assemblies against the nano - bulks and thered shift of the luminescence peaks were discussed.
Based on the structural model of multiple entangled transient networks and the mechanism of multiple reptation by dynamic reorganization of entanglements,the probability distribution function of the end - to - end vector for entangled constituent chain,the conformation probability distribution function of entangled polymer chain,the visco - elastic free energy of deformation of polymeric melts under stress, and the recoverable visco - elastic free energy of deformation of extrudates without stress were calculated by the combined method of statistical mechanics and kinetics. A new molecular theory of visco - elasticity of recoverable strain for extrudates of polymers was proposed. The memory function and elastic modulus were derived from the molecular theory of visco - elasticity of recoverable strain for extrudates of polymers. When the memory function is introduced into the O - W - F type of constitutive equation with the Cauchy - Green and Finger tensors for simple strain shear fluid,then the dependence of viscosity and first normal - stress difference coefficient on shear rate was formulated. A new method for determining the visco- elastic parameters(η0,GN and ψ10)and the topologically constrained dimension numbers( n' and a)was used to study on the relations of recoverable strains to the conditions of extrusion. It is well known that the total strain consists of elastic and visco - elastic strains,when the unified structure parameter of the fraction of trans - isomer conformation of polymer chains under elastic and viscoelastic strain state is introduced into above expressions of free energy of deformation. A new relationship between the recoverable strain and the swelling ratio for extrudates is obtained and a new equation of swelling ratio for extrudates was derived. At the same time,based on the material function a set of new relationships between the recoverable strain( SR)with the condition of extrusion[temperature,rate of extrusion,extrusion die and length to diameter ratio( L / D)]and the primary structure of resins was developed. These equations were verified by a great amount of experimental data. It shows that they are an excellent agreement between theese theoretical equations and experimental data.
This paper induces alternate field of elastic theory into electomagnetics,from the first principle,sets up an integral equation of determining electric field in composite by border condition imitatingand Fourier analysis,further studies its electrical conductivities,theoretical result is identical with experimentalvalue. The method of this paper is not limitted by particle density and system structure,it opensa new way about studying the conductance of composite.
Many different properties of floating and deposited DDAC films have been introduced,especiallyintroduced the nonlinear variation of conductance on DODAC multilayers. As a fabric softener,thecapability of dissipating static charge which obtained by using a Scorotron arrangement,is also very important.In this paper,another electrical property charge decay under different relative humidities(RH)is reported. The percolation theory applied in previous paper is again employed here to interpret the nonlinearrelationship between charge decay and RH. The experimental data show that there are two steps forthe decay;the first step is quite fast within the initial 30 min,after that is a rather slow step. AlthoughDDAC is an insulating material,it has very strong ability to absorb moisture from the atmosphere,thismakes DDAC a better conductance than polyester. According to the measurement of electrical propertiesof DDAC,it is not only a very good fabric softener but also a good conducting material under the conditionsof high relative humidities.
Oxygen permeation through dense SrFe1.125Co0.375Oy membranes was studied by exposing one side of the membranes to flowing air and the other side to the mixture of CO and helium. The oxygen permeation flux reached as large as 6.0 × 10- 7mol / cm2s at 900℃. The oxygen permeation showed a weak temperature dependence at temperatures about 850℃. The oxygen flux increased linearly with increasing CO partial pressure and remained almost constant with variation of the membrane thickness. These observations all indicate that the overall oxygen permeation process is limited by the surface reaction at the membrane surface exposed to CO.
The effects of temperature and time on the nature of carbon deposition over Ni / Al2O3 catalyst were investigated using an on - line quadruple mass spectrometer method. The experimental results suggested that the initial carbon species,viz. NiXC,produced by CH4 decomposition over reduced Ni / Al2O3,trends to diffuse into the bulk at lower temperature(600700℃)and to transform into more inactive carbon species at higher temperature(700800℃)and longer duration. The catalyst deactivates quickly for CH4 decomposition at higher temperature due to the blocking of active sites by immobile carbon species.
The kinetics and thermodynamics of hexadecylpyridiumchlorid in solvent sublation were studied.With the measurement of the surface forces at different temperatures and concentration,the freestandard adsorption energy ΔG0adswas obtained with - 33. 17kJ / mol. The process of solvent sublation ofhexadecylpyridiumchlorid is obedient to first order kinetics. The apparent rate coefficient decreases withthe increase of experiment temperature but increases with the increase of the air flow rates.
A theory for solvation thermodynamics of binary solution is developed by Virial expansionmethod. The excess energy of binary solution is divided into three interactive terms of solvent - solventsolvent - solute and solute - solute. Using the approach of Virial expansion the partial function of canonicalensemble for a binary solution is expressed. The expression of partial molar energy and entropy of soluteare obtained by this expression. Under the condition of infinite dilution,the solvent - solvent term ofthe excess partial molar energy can also be called as reorganization energy. It shows that the presentationof solute affects interactive energy of solvent molecules around solute molecules. The study in this papershows that when the molar fraction of solute particles is relatively higher,the interaction among solutemolecules would affect the solvent - solvent term of excess partial molar energy. For diluted solution,thesolvent - solvent term of excess partial molar energy is linear to the molar fraction of solute. For binarysolution with low density,the excess partial molar energy and excess partial molar entropy of solute is alsolinear to the density of particles.