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Vol. 26, No. 6 (1977)

1977-03-20
CONTENT
MULTICENTRE VARIATIONAL MODEL FOR STUDYING THE CLUSTER FORMATION OF Be8 AND Li6
WU GUANG-HAN, LU ZHAO-QI
1977, 157 (6): 459-466. doi: 10.7498/aps.26.459
Abstract +
A multicentre variational model is proposed for the study of nuclear cluster forma-tion. The binding energies of Be8 and Li6 have been calculated and found to be in agreement with experiment.
SYMMETRY CLASSIFICATION FOR EXCITED STATES OF HYPERNUCLEI
ZHANG ZONG-YE, LI GUANG-LIE
1977, 157 (6): 467-476. doi: 10.7498/aps.26.467
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The method which Wigner used for the classification of supermultiplets has been generalized to the excited energy spectrum of hypernuclei. The general form of two-body interaction is obtained which approximately does not break the SU6=SU3?SU2 classification and the coefficients in each of its term are determined from the experimental scattering data. The formula for the energy matrix element under SU6 is also derived. For 9ΛBe*,10ΛBe* and 10ΛΛBe*, some concrete calculations aregiven. We find that 9ΛBe* states seem to agree qualitatively with experiment.
GENERALIZATION OF QUANTUM EXPANSION OF SOLITON SOLUTIONS
YIN PENG-CHENG
1977, 157 (6): 477-485. doi: 10.7498/aps.26.477
Abstract +
As a means of establishing a soliton model based on gauge fields for hadrons, the quantum expansion method for soliton solutions recently propesed by T. D. Lee has been generalized to cover more general systems including gauge fields. Our results are similar to those obtained by T. D. Lee, but some of our quantities have a broades content, as in formula (33) - (37).
AN IONIC GROUPING THEORY OF THE ELECTRO-OPTICAL AND NON-LINEAR OPTICAL EFFECTS OF CRYSTALS (Ⅲ)——A THEORETICAL CALCULATION OF THE ELECTRO-OPTICAL AND OPTICAL SECOND HARMONIC COEFFICIENTS FOR LiNbO3, LiTaO3,KNbO3, AND BNN CRYSTALS BASED ON A DEFO
CHEN CHUANG-TIAN
1977, 157 (6): 486-499. doi: 10.7498/aps.26.486
Abstract +
Based on (MO6) ionic grouping model as previously proposed in (I), we have calculated the various electro-optical coefficients as well as the optical second harmonic coefficients for LiNbO3, LiTaO3, KNbO3, and BNN crystals. If we assume that the oxygen-octahedra in the crystal lattice of these crystals of Oh symmetry all possess the same energy level and wavefunctions, then the energy level and the wavefunction for LiNbO3, LiTaO3, KNbO3, and BNN erystals of C3ν, or C2ν symmetry can be found upon applying the theory of group representations. Furthermore, by using the ABDP theory, we have calculated their electro-optical and optical second harmonic coefficients. It is interesting to note that without introducing any adjustable parameters the calculated values agree satisfactorily with the experimental data. The dependence of the magnitude and the sign of the optical second harmonic coefficients for these crystals upon the degree of the oxygen-oetahedra distortion has also been interpreted theoretically in this paper. We have thus arrived at the following conclusions:(1) The ionic grouping theory of the deformed oxygen-octahedra model proves to be appropriate not only for the perovskite-type structure but also for the tungsten bronze and LiNbO3 type structures.(2) In crystals of the tungsten bronze and LiNbO3 type structure, it is the ionic bonds that make major contribution to the electro-optical and optical second harmonic effects. As the covalent nature of bonds in the LiTaO3 crystal exceeds that in the LiNbO3 crystal, the non-linear optical effects in the LiTaO3 erystal are weaker than those in the LiNbO3 crystal.(3) The magnitude and the sign of the optical second harmonic coefficients for these crystals depend upon the degree of the oxgen-octahedra distortion.
THEORETICAL ANALYSIS OF THE ELECTRICAL CONDUCTION AND DIELECTRIC BEHAVIOR OF α-LiIO3 SINGLE CRYSTALS
LI TIE-CHENG, XU ZHENG-YI
1977, 157 (6): 500-508. doi: 10.7498/aps.26.500
Abstract +
By using the Debye-Hückel equation and the Poisson equation, the almost one-dimensional ionic conductive behaviors of α-LiIO3 have been analysed theoretically. The current across the boundaries between the crystal and metallic electrodes is con-sidered to be limited by rate processes. The asymmetry of the ± c-directions due to spontaneous polarization of the crystal has been taken into consideration. The explicit expression derived for the apparent DC conductivity is satisfactory in explaining the characteristic behavior of α-LiIO3, e.g., the dependence of conductivity on applied voltage, as shown experimentally in [1]. The functional relationship between the AC dielectric constant and the bias field (cf. [1]) is interpreted partially by following the approach given in [2]. It is also pointed out that the weak current constantly flowing through the wire connecting the end surfaces of opposite polarity of an α-LiIO3 single crystal (cf. [3]), as well as similar phenomena observed in our own laboratory on poled ferroelectrics such as BaxSr1-xNb2O6(x~1/3), are caused by the crystal-line polarity EMF. This EMF coexists with the spontaneous, polarization Ps.
THEORY OF THE SUPERCONDUCTING CRITICAL TEMPERATURE (Ⅰ)
WU HANG-SHENG, CAI JIAN-HUA, GONG CHANG-DE, JI GUANG-DA, CAI JUN-DAO
1977, 157 (6): 509-520. doi: 10.7498/aps.26.509
Abstract +
In this paper, we have solved the Eliashberg equation for T=Tc, obtaining a series expression for the superconducting critical temperature Tc=α0(μ*)(λ〈ω2〉)1/2{1+1/λα1(μ*)〈ω4>/〈ω2>2+1/λ2(α21(μ*)〈ω6>/〈ω2>3+α22(μ*)〈ω4>2/〈ω2>4) +1/λ3(α31(μ*)〈ω8>/〈ω2>4+α32(μ*)(〈ω4>〈ω6>)/〈ω2>5)+α33(μ*)〈ω4>3/〈ω2>6+……}, where α0(μ*), α1(μ*) etc. depend upon μ* only. This new Tc formula shows that Tc is determined not only by λ, 〈ω2〉 and μ*, but also by the various moments 〈ω2n〉 of the effective phonon spectrum.
BRIEF REPORT
X-RAY DIFFRACTION UNDER HIGH PRESSURE
XU JI-AN, HU JING-ZHU
1977, 157 (6): 521-525. doi: 10.7498/aps.26.521
Abstract +