共查询到20条相似文献,搜索用时 15 毫秒
1.
The elastic interaction of two point defects in cubic and hexagonal structures has been considered. On the basis of the exact expression for the tensor Green’s function of the elastic field obtained by the Lifschitz–Rozentsveig for a hexagonal medium, an exact formula for the interaction energy of two point defects has been obtained. The solution is represented as a function of the angle of their relative position on the example of semiconductors such as III-nitrides and α-SiC. For the cubic medium, the solution is found on the basis of the Lifschitz–Rozentsveig Green’s tensors corrected by Ostapchuk, in the weak-anisotropy approximation. It is proven that the calculation of the interaction energy by the original Lifschitz–Rozentsveig Green’s tensor leads to the opposite sign of the energy. On the example of the silicon crystal, the approximate solution is compared with the numerical solution, which is represented as an approximation by a series of spherical harmonics. The range of applicability of the continual approach is estimated by the quantum mechanical calculation of the lattice Green’s function. 相似文献
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The propagation of elastic waves in an arbitrary direction through a hexagonal piezoelectric crystal is investigated. Orientational relations are obtained in analytic form for the effective elastic moduli and the piezoelectric and dielectric constants, and also for the basic parameters of the elastic waves: the phase velocity, electromechanical coefficient, and the divergence between the displacement vector and the energy flux. Expressions are given for the directions in which the electromechanical coefficient takes an extremal value, and the basic parameters are calculated for cadmium sulfide.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 101–105, May, 1977. 相似文献
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A survey is made of pairs of heteronormal planar elastic waves, which can propagate in an unlimited crystal medium and have equal theoretical values of the phase velocity, using Voigt elastic moduli. Such pairs are chosen for which it is possible that the theoretical equality of velocities will be disturbed when using another theory of the elastic properties of crystals with generally different tensors of material constants (for example Kuvshinskij J. V., Aero E. L.: Fiz. tv. tela5 (1963), 2591). In such a case, a comparison of the measured velocities of a suitable pair of waves can help to decide between the two theories. Pairs of waves are found for 12 non-piezoelectric crystal classes. Among such pairs it is easy to find pairs of waves of the same properties for piezoelectric crystal classes. 相似文献
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J.T. Yu 《Journal of Physics and Chemistry of Solids》1976,37(3):301-303
Electron paramagnetic resonance has been observed for Dy3+ in ZnSe and Tm3+ in CdS. For Dy3+ doped ZnSe, an isotropic spectrum was observed having well resolved hyperfine lines due to 161Dy and 163Dy. The g value obtained was 6.577 ± 0.002 and 161A was 191 ± 1 × 104 cm?1 and 163A was 265 ± 3 × 10?4 cm?1. The agreement of the observed g value to g(τ6) = 6.667 and the point-charge calculations suggest that Dy3+ occupies an interstitial (II) site with no local charge compensation. For Tm3+ doped in hexagonal CdS, an axial spectrum consistent with g⊥ = 0, g∥ = 10.722 ± 0.007, D = 2.57 GHz (crystal field splitting) and 169A = 1207 ± 5 × 10?4cm?1. The large g∥ value indicates that the Tm ion exits in the trivalent state. This is in reasonable agreement with previous reports of the non-Kramer's state of Tm3+. 相似文献
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A simplified phenomenological theory of the temperature dependence of the second-order elastic constants of crystals is considered.
The temperature dependences of the second-order elastic constants are calculated for a series of cubic crystals with various
types of predominant chemical bonding. Satisfactory agreement between the calculation results and experimental data is obtained.
Fiz. Tverd. Tela (St. Petersburg) 41, 235–240 (February 1999) 相似文献
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Experimental studies (by the ultrasonic pulse method) and theoretical investigations (with the model of polarizable ions) were made of changes in the elastic moduli of single crystals of NaCl, NaBr, NaI, KCl, KBr, and KI in cubic hydrostatic compression in the pressure range up to 108 Pa at a temperature of 298°K. The experimental unit and method of measurement are described. Theoretical values of the derivatives of the elastic moduli with respect to pressure are presented for the compounds studied and are compared with existing empirical data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 71–75, October, 1985. 相似文献
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The paper deals with a detailed numerical study of the sections of the inverse and ray velocity surfaces for cubic crystals.
The figures for the sections of the inverse and ray surfaces by the (001) and (110) planes have been plotted for over 65 crystals
and from these, the nature of the cuspidal edges has been discussed. Typical graphs of the inverse and ray surfaces have been
given. The parameters characterising the dimensions of the cusps have been tabulated. It is shown that the A-15 compounds
exhibit very unusual and interesting wave surfaces at temperatures below superconducting critical temperatures. 相似文献
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M. Sh. Akchurin R. M. Zakalyukin I. I. Kupenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(3):485-487
The role of twinning processes giving rise to the fragmentation and rotation of a structure caused by single-crystal deformation, as well as the joining of grains during the manufacturing of optical ceramics, is investigated. Models describing the twins in the single crystals under study, which are formed by rotating a cubic lattice about the threefold symmetry axis through an angle of 60°, are constructed. The twin formation energies are estimated. 相似文献
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V. Yu. Ivanov A. A. Mukhin A. S. Prokhorov A. M. Balbashov L. D. Iskhakova 《Physics of the Solid State》2006,48(9):1726-1729
DyMnO3 single crystals of hexagonal modification were grown for the first time by zone melting, and their anisotropic magnetic properties were studied in detail. At T ~ 7 K, a small uncompensated magnetic moment (~1 μB per formula unit) is shown to occur along the hexagonal axis. At temperatures 7–45 K, a transition from the purely antiferromagnetic state to a state with uncompensated magnetic moment was revealed; the transition is induced by a magnetic field H parallel to the c axis. This transition seems to be due to a ferrimagnetic ordering of the moments of Dy cations located in nonequivalent crystallographic positions. 相似文献
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V.G. Plekhanov G.S. Zavt T.A. Betenekova A.A. OConnel-Bronin S.O. Cholakh 《Solid State Communications》1978,25(3):159-161
The shape of one-phonon sidebands of exciton in LiH is studied both in reflection and edge luminescence spectra. The main structure of the shape is found to reflect the phonon density of states. This fact is interpreted as a result of a high anisotropy of the exciton band. 相似文献
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V. Prosser 《Czechoslovak Journal of Physics》1960,10(4):306-316
The optical constants of single crystals of hexagonal selenium in the region of the intrinsic absorption edge in polarized light were investigated. The absorption edge for light polarized normal to the optical axis of the crystal is displaced towards longer wavelengths. The absorption maximum of hexagonal selenium for a wavelength of 0·6 is interpreted as the maximum corresponding to interaction between neighbouring chains and in connection with this the position of the absorption edge of different modifications of selenium is discussed.
In conclusion the author wishes to thank Dr. E. Klier and R. Kuel for valuable discussions and advice. He thanks laboratory assistants J. Ontl and O. Kundrátová for help in the work. 相似文献
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In conclusion the author wishes to thank Dr. E. Klier and R. Kuel for valuable discussions and advice. He thanks laboratory assistants J. Ontl and O. Kundrátová for help in the work. 相似文献
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A. E. Puro 《Optics and Spectroscopy》2014,117(3):406-410
A method for determining residual stresses in elongated transparent blanks of hexagonal single crystals the optical axis of which is directed along the crystal is proposed. It is assumed that the residual deformation tensor is of thermal character and is characterized by a fictitious temperature. Characteristic parameters of polarized light have been measured by the tomographic method in the plane orthogonal to the single crystal axis. 相似文献
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W. Maysenhölder 《Physics letters. A》1984,100(6):289-292
The Eshelby factor for cubic crystals has been calculated for arbitrary anisotropy. One of the two integrations needed could be performed analytically. An expansion up to 4th order in the anisotropy and exact results for special cases are also given. 相似文献
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The polarization of the IR luminescence of oriented ZnS crystals has been measured. None of the three main emission bands shows measurable polarization after excitation with polarized or unpolarized light. This result supports centers with symmetryT d because they do not require any selection rules for the polarization of optical dipole transitions. 相似文献
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I. Ursu L. C. Nistor V. S. Teodorescu S. V. Nistor I. N. Mihailescu N. N. Kolesnikov V. I. Konov M. P. Kulakov Yu. M. Starodumov N. I. Chapliev V. E. Shub 《Applied Physics A: Materials Science & Processing》1989,48(5):451-456
A microscopy study of the morphology of the damage produced by TEA-CO2 laser pulses in cubic ZnSe single crystals grown from melt is presented. The observed bulk filamentary damage consists of relatively uniformly distributed elementary damaged zones, located at specific sites where absorbing inclusions could exist. Transmission electron microscopy and laser ion mass spectroscopy investigations revealed the absorbing inclusions to be thin graphite foils, originating from the crucible used for crystal growth. 相似文献
18.
Ultrasonic wave velocities have been measured by the pulse echo technique at 15MHz in single crystals of InBi grown by zone-melting. The elastic stiffness constant set has been computed from the velocity data by a least-mean-squares procedure. The elastic behaviour of this metallic compound is quite different in kind from that of the semiconducting III-V crystals; the volume compressibility does not follow Keyes' generalisation for the other III-V compounds. The elastic properties of InBi have been found to show the characteristics of a layer-like crystal with weak interlayer binding; this finding is illustrated by the linear compressibilities and by a compilation of cross-sections of the wave velocity and Young's modulus surfaces. The Debye temperature is 115°K. 相似文献
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Joginder N. Anand 《Journal of Macromolecular Science: Physics》2013,52(3):445-458
Polyethylene has an orthorhombic lattice for which nine elastic constants exist; they are obtained in terms of the intra- and intermolecular forces. Constants involved in the 6-12 Lennard-Jones potential approximating the London dispersion type of van der Waals' forces are obtained by computing the crystal potential energy and comparing it with the cohesive energy. First and second nearest-neighbor interactions are considered to establish relationship between the elastic constants and the interaction constants. The latter are obtained in terms of the C—C bond, stretching, bending, and repulsive force constants and the L-J potential constants. A limited type of central force assumption is applied. Values of Young and shear moduli are obtained along the three axes. The value along the chain compares with the experimentally determined and calculated values for oriented polyethylene. Young's modulus along the lateral direction is of the order of Young's modulus of bulk polyethylene, showing that intermo-lecular forces are the ones that determine the Young modulus of bulk polyethylene. 相似文献