Vol. 47, No. 4 (1998)
1998, 47 (4): 529-535. doi: 10.7498/aps.47.529
In this paper a Mbius inversion transform formula is proposed and proved for a crystal with hcp structure.By the use of the formula the pair potential can be converted from the cohesive energy.As an example,the pair potential in magnesium is calculated and discussed.
1998, 47 (4): 536-541. doi: 10.7498/aps.47.536
In this paper,the Schrdinger equation with an anharmonic oscillator potential V(x)=x2/2+g/2x2 is solved.The exact energy equation and the normalized wave function are obtained.The double-wave function quantum theory is applied to gain the time evolution equation to describe the physical quantities of a single motional particle in the anharmonic oscillator.
1998, 47 (4): 542-550. doi: 10.7498/aps.47.542
By taking into account the influence of the concentration of particles n,diffusive range Δ,the probability of reaction P and maximum diffusive steps W,the diffusion and reaction-limited aggregation with finite steps model is presented.The varied patterns of aggregation and their fractal dimension are obtained under condition of nearest-neighbor.The results show that the form of aggregation is discrete cluster at lower n.However,the growth morphologies change from discrete cluster to continuous dendrite with the increase of P or W at higher n.
It is indicated that when observing the phenomenon of quantum chaos with the help of energy-level curves,except an energy-unfolded spectrum to be required,an unfolding procedure for the curve parameter should be considered too.A general method for the parameter unfolding could be realized by normalizing the mean-square-root of slopes of level curves.If the curves are in average declined,an energy shift is also needed for eliminating this,before the parameter unfolding process is carried out.Discussions of the curvature of so unfolded level-curves are made,in connection with the Gaspard-Rice-Mikeska-Nakamura's formula of dimensionless curvature.
INFLUENCE OF THE CYCLIC STRAIN WAVEFORM ON THE ULTRASONIC ATTENUATION DURING THE FATIGUE PROCESS OF ALUMINIUM
1998, 47 (4): 559-563. doi: 10.7498/aps.47.559
The ultrasonic attenuation Δα has been measured during the fatigue process of aluminium which is controlled by the total strain with a triangular or a sinusoidal waveform.The results indicate that the waveform has an influence on the Δα-ε curve at low strain amplitude,but has little influence at high strain amplitude.At low strain amplitude,the major reason causing the variation of Δα is the interaction between dislocations and point defects,and the waveform can change the re-distribution of point defects at the average stress field of the vibrating dislocation segments,as a result,the stable Δα-ε curves for the two kinds of waveform are different.At high strain amplitude,dislocation multiplication occurs,the interaction between dislocation segments is dominant,and the waveform cannot influence the dislocation multiplication and the interaction between dislocation segments.
1998, 47 (4): 564-570. doi: 10.7498/aps.47.564
The invariant velocity spectra of the forward emitted fragments in the 25MeV/u40Ar induced reactions are investigated,their parallel momentum and reduced parallel momentum distribution widths of the fragments are extracted.Furthermore,the emitted products are summarized.
ATOMIC AND MOLECULAR PHYSICS
1998, 47 (4): 571-576. doi: 10.7498/aps.47.571
The dynamical process of interaction of the 1D H+2 with an ultra-short intense laser pulse is studied with a pure classical theory.Using the classical statistical method,we investigate numerically the evolutions of the probabilities for excitation,dissociation,ionization and dissociative ionization,and analyse the calculated results.
1998, 47 (4): 583-590. doi: 10.7498/aps.47.583
A distorted-wave Born exchange (DWBE) approximation is used to calculate the cross sections of electron-impact ionization for Ne+,…，Ne6+.The comparison shows good agreement between theoretical and experimental results.We give empirical formulas with high precision to meet the requirements of applications.The validity of the DWBE method in lowly ionized ions and the affect of the exchange potential on the calculated results are also discussed.
1998, 47 (4): 591-597. doi: 10.7498/aps.47.591
This paper presents a molecular dynamics simulation for the atomic structure of nanocrystalline copper.The density,energy distribution,X-ray diffraction patterns and radial distribution function were calculated as functions of grain size in the nanocrystal.The results show that the large volume fraction of the boundaries and the distortion of the grains make the properties of nanocrystals different from those of materials consisting of coarse grains.
CLASSICAL AREA OF PHENOMENOLOGY
1998, 47 (4): 598-605. doi: 10.7498/aps.47.598
We have discussed the recording of moving grating in photorefractive materials at large modulation depths using hopping model.The analytical expressions of the first three-order spatial charge field are presented which describe the nonstatic recording of the moving fringes.And the dependence of the space charge field on the veloctiy of the moving fringes is discussed for non diffusive field.We found that the higher-order harmonics of the space charge field for low diffusive field can be selectively enhanced with applied small dc field.Otherwise,they cannot be selectively enhanced if the diffusive field is large than the applied electric field.
1998, 47 (4): 606-612. doi: 10.7498/aps.47.606
The invariant-related unitary transformation method is used to study the transference of a kind of nonclassical properties between two interacting modes of light.With the aid of numerical computation,it is interesting to find that the mutual conversion of the Fock states (being nonclassical) and the coherent states is attained when the interaction is chosen appropriately.
1998, 47 (4): 613-618. doi: 10.7498/aps.47.613
Absolute diffraction efficiencies of a transmission grating at a photon energy of 844eV have been calibrated on synchrotron radiation source.With the aid of grating model,all structure parameters of the grating are obtained and absolute diffraction efficiencies for soft X-rays in the range of 100—2000eV are calculated and discussed.
THEORETICAL AND EXPERIMENTAL STUDY ON COMPRESSION OF CHIRPED OPTICAL PULSES UTILIZING DISPERSION-COMPENSATION AND HIGH-ORDER SOLITON EFFECT
1998, 47 (4): 619-624. doi: 10.7498/aps.47.619
In this paper,we study theoretically and experimentally the compression of chirped optical pulses in dispersion-compensation fiber and dispersion-shifted fiber utilizing single mode rate equation of semiconductor laser and nonlinear Schrdinger (NLS) equation.In experiment,the 53.8ps pulses generated by a gain-switched DFB semiconductor laser diode with 2.5GHz repetition rate were compressed to 12ps in a length of dispersion-compensation fiber.Then,the 12ps pulses were compressed to 2.5 or 2.1ps due to high-order soliton effect in dispersion-shifted fiber.Experimental results agree with theoretical results.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
In this paper a detailed study is performed to the ionic abundance in hot plasmas at definite temperatures and densities of matter by employing both the theory f fluctuation of entropy and Boltzmann relation on the relativistic Hartree-Fock-Slater self-consistent field average atomic model.A convolution method for fast calculation of ionic abundance is presented.The degree of ionization and ionic abundance following the changes of temperature and density of matter is discussed by taking gold as an example.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
We reviewed recent theoretical and experimental results on the polymerization of solid C60.The characteristics in common of several methods and the difference between each other are analyzed.Orientational disorder always plays an important role in polymerization,because two C60 molecules must be located at a specified relative position before cycloaddition reaction.
ANALYSIS AND SIMULATION OF FLUORINE MIGRATION CHARACTERISTICS OF BF+2-IMPLANTED INTO POLYCRYSTALLINE SILICON GATE
1998, 47 (4): 645-651. doi: 10.7498/aps.47.645
The migration equation of fluorine in polycrystalline silicon gate is presented on the basis of analysis for the migration characteristics of fluorine in polycrystalline silicon gate after BF+2 is implanted into polycrystalline silicon gate.The distribution of fluorine in polycrystalline silicon gate is simulated by the finite difference methods.The simulation results are in good agreement with the experiments.Under the condition of 80keV,2×1015cm-2BF+2 implanted into polycrystalline Si gate and then annealed at 900℃ for 30s,some important coefficients are given as follows: emisson coefficient of fluorine in polycrystalline silicon e=6×10-2s-1,diffusion coefficient of fluorine in grain boundary Db=7.64×10-12cm/s,absorption coefficient of fluorine in polycrystalline Si/SiO2 interface S1=1.74×10-3s-1 and damage absorption coefficient of fluorine in polycrystalline silicon S1=7.32×10-4s-1.
1998, 47 (4): 652-657. doi: 10.7498/aps.47.652
The atomic configuration and electronic structure of erbium-doped silicon are studied theoretically by using local density formalism (LDF) and discrete variational method (DVM).The influence of codoping with oxygen is also investigated.The minimum-energy atomic configuration is that erbium occupies a tetrahedral interstitial site for an isolated erbium atom.In this configuration,Er 5d levels are located near the conduction band edge of Si in shallow resonance states. With the presence of oxygen,the binding energy of the structure decreases. In this case,the minimum-energy atomic configuration is that erbium occupies a hexagonal interstitial site with six nearest neighbors of oxygen atoms. An electronic state caused by the hybridization of Er 5d,O 2p and Si 2p electrons is located 0.3eV below the conduction band edge,which might be correlated with the deep level at Ec-0.15eV observed by the experimental measurement in Er and O codoped Si.
1998, 47 (4): 658-663. doi: 10.7498/aps.47.658
The expressions of internal friction values of four mechanical models and corresponding vibration systems have been deduced.The relationships between the internal friction values of the specimen and the vibration system for two-parameter models and two models of the standard anelastic solid have been obtained.It is found that these relationships for different models or the materials of different mechanical properties are different.
1998, 47 (4): 664-671. doi: 10.7498/aps.47.664
An expression concerning the variation of the pitch of SmC* liquid crystals is obtained by using the cell model in statistical mechanics with the introduction of the distribution factor ζχ of the chiral centers in the interaction potential between biaxial molecules containing multiple chiral centers.It shows the condition for inversion of helicity of the liquid crystals.With proper choice of the values of parameters involved we have calculated the variation of the pitch with temperature for liquid crystals TDOBAMCC,FLC,PACMB and H6/10.The calculated results agree well with the experimental data.
ORIENTATIONALLY ORDERED STATE AND REORIENTATION RELAXATION IN SOLID C60 AT HIGH PRESSURE AND LOW TEMPERATURE
1998, 47 (4): 672-677. doi: 10.7498/aps.47.672
The distribution of the orientationally ordered structure and reorientation relaxation behavior in solid C60 at high pressure and low temperature have been investigated by using a model of the classical molecular interaction between C60 molecules.The anomalous behavior in thermal conductivity experiment can be well explained theoretically.
1998, 47 (4): 678-685. doi: 10.7498/aps.47.678
Self-diffusion of adatoms on Ag,Pt,Au(110) surfaces is investigated with the surface embed-ded atom method(SEAM) and molecular dynamics.By quenched molecular dynamics,the static energy variation and the pathway of the atoms for hopping and exchange mechanisms are obtained.The self-diffusion characteristics of these metals are analyzed,and the results show that the diffusion is isotropic on Pt(110) surface but anisotropic on Au,which are in accordance with the observation in experiments.
1998, 47 (4): 686-691. doi: 10.7498/aps.47.686
Two kinds of Cu substrates were used to grow diamond films,one of them being 99.99% polycrystalline Cu foil and the other 99.95% phosphorus deoxidized Cu foil.Large-area,free-standing polycrystalline diamond films were obtained by hot filament CVD on both substrates.The diamond films on the two kinds of Cu substrates were comparatively investigated by high resolution optical microscopy,scanning electron microscopy,Raman spectroscopy,and X-ray diffraction.The quality of films on deoxidized Cu are not worse than that on polycrystalline Cu,while the nucleation densities ,growth rate and stress in film on deoxidized Cu is higher than those on polycrystalline Cu.It is indicated that the annealing process and optimized growth conditions must be used to obtain large-area continuous diamond films.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1998, 47 (4): 692-698. doi: 10.7498/aps.47.692
Synchrotron radiation photoemission and ferromagnetic resonace(FMR) measurement have been used to study the interface formation of Co/GaAs(100) as well as the magnetic property of ultrathin Co films.The results show strong interface disruption and reaction between overlayer and substrate at low Co coverage(～0.2nm),At the coverage of 1nm,a stable interface forms.The Ga atoms in bulk GaAs may exchange with Co atoms and diffuse into Co overlayer,while a certain amount of As reacts with Co atoms,forming stable Co-As bonding.These reaction products lie in the narrow region near the interface(0.3—0.4nm).The remanent part of As will segregates on the surface of Co overlayer.Based on a theoretical model,the interface structure and concentration profile are discussed in detail.The FMR result demontrates that the ultrathin Co film consists of good-quality crystals and has a chemical homogeneity.
1998, 47 (4): 699-704. doi: 10.7498/aps.47.699
The diode consisting of nano-silicon quantum dots embedded in an amorphous silicon matrix was fabricated and the discontinuous staircases on its I-V curves were observed.There were two distinct regimes on I-V curves of diode:(i) the sequential tunneling regime,where current increased monotonously with increasing negative bias;(ii) the resonant tunneling regime,where the current increased dramatically with increasing negative bias,and three quantum staircases appeared.It was found that the steps was related to the grains of the deposited film.The qualitative explanation of this physical phenomenon was proposed in terms of the material structural characteristics.