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771.
I. V. Bodnar 《Journal of Applied Spectroscopy》1998,65(3):466-468
Raman spectra in (┴, ┴) and (║, ║) polarizations are investigated on crystals of CuGaS2, AgGaS2 compounds and CuxAgl−xGaS2 solid solutions. The frequencies of longitudinal and transverse optical phonons are determined, their concentration dependences
are constructed, and the behavior of the vibrational modes in CuxAgl−xGaS2 solid solutions is established.
Belarusian State University of Information Science and Radioelectronics, 6P, Brovka St., 220069, Minsk, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 447–449, May–June. 1998. 相似文献
772.
D. Staresinic A. Borovac K. Biljakovic H. Berger F. Levy J.W. Brill 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):425-429
We report on measurements of the voltage dependence of the complex shear compliance of two crystals of the charge-density-wave
(CDW) conductor NbSe3, for torsional frequencies between 1 Hz and 71 Hz. For both samples, there is a frequency independent, ∼1% increase of the magnitude of the compliance when the voltage exceeds the threshold for CDW depinning, but the internal
friction has a striking sample dependence which we do not understand. For one sample, there is a frequency independent decrease
in internal friction with CDW depinning, suggesting that the elastic changes are not relaxational and might reflect changes
in the screening of the crystal strain by the CDW. For the second sample, the sign and magnitude of the change in internal
friction is strongly frequency dependent, which we associate with a change in screening due to the finite electron diffusion
time. The second sample also exhibits a frequency dependent peak in internal friction near threshold that may reflect relaxation
of the CDW phase.
Received 14 August 2001 and Received in final form 3 October 2001 相似文献
773.
H. Nienhaus V. van Elsbergen W. Mönch 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(2):179-182
Si-terminated 3C-SiC(001) surfaces with () and ()reconstructions were investigated by high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron diffraction
(LEED) and Auger electron spectroscopy. The surfaces were prepared by subsequent annealing steps after cleaning by heating
in a Si flux. At ()-reconstructed surfaces, the HREELS intensity increases while the widths of the loss lines decrease with proceeding preparation.
Eventually, weak loss structures at 380 and 700 cm-1 are detected besides the strong Fuchs-Kliewer phonon loss peaks. They are attributed to surface-localized vibrations, i.e., to stretching modes of on-top Si dimers and of C-Si-C groups, respectively. The weak features vanish after exposure to atomic
deuterium, but reappear after subsequent annealing. At () reconstructed surfaces the HREELS lines are broadened and no surface-localized modes were resolved.
Received 18 January 1999 相似文献
774.
In the current research paper, a conservative system comprising of a mass grounded by linear and nonlinear springs in series connection is studied. The equation of motion for the aforementioned system has been derived as a nonlinear ordinary differential equation with inertia and static–type cubic nonlinearities. The global residue harmonic balance method is applied to obtain an approximate analytical frequency and periodic solution of the problem. Using the obtained analytical expressions, the influences of the hardening and softening nonlinear spring on the non–dimensional frequency are investigated. The results show that developing the system nonlinearity leads the displacement of the mass and the deflection of linear spring to approach each other. Moreover, comparison of the results obtained using the proposed procedure with those achieved by other methods such as numerical method, variational iteration method and harmonic balance approach demonstrates the accuracy and advantages of the current approach. 相似文献
775.
利用密度泛函理论的平面波赝势方法研究了IrTi合金的晶格动力学行为. 声子谱计算表明四方(L10)结构动力学不稳定,通过冷冻不稳定声子模式, 发现IrTi会发生从四方(L10)到正交的结构相变.进一步分析软模对应的原子振动, 得到了具有正交对称性,空间群为Cmmm,相对于四方(L10)相能量更低、更稳定的结构. 这种正交新相(Cmmm)弹性稳定和动力学稳定,而且其结构参数与实验上观察到的低温结构有限的晶格参数相符合,表明IrTi合金的低温相是正交结构(Cmmm). 从理论上肯定了IrTi合金立方到四方再到正交的相变机制, 解决了实验上关于相变机制和低温相结构形式的争议. 相似文献