共查询到20条相似文献,搜索用时 15 毫秒
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We measured the dispersion of the graphite optical phonons in the in-plane Brillouin zone by inelastic x-ray scattering. The longitudinal and transverse optical branches cross along the Gamma-K as well as the Gamma-M direction. The dispersion of the optical phonons was, in general, stronger than expected from the literature. At the K point the transverse optical mode has a minimum and is only approximately 70 cm(-1) higher in frequency than the longitudinal mode. We show that first-principles calculations describe very well the vibrational properties of graphene once the long-range character of the dynamical matrix is taken into account. 相似文献
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The phonon dispersion relations in NiO have been measured using coherent inelastic neutron diffraction. Good fits to the data were obtained using various shell models. The room temperature phonon density of states was calculated and used to determine the temperature dependence of the lattice specific heat and the Debye temperature. 相似文献
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L. A. Falkovsky 《Journal of Experimental and Theoretical Physics》2007,105(2):397-403
Taking into account the constraints imposed by the lattice symmetry, we calculate the phonon dispersion for graphene with
interactions between the first and second nearest neighbors. We show that only five force constants give a very good fitting
to the elastic constants and phonon frequencies observed in graphite.
The text was submitted by the author in English. 相似文献
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C.M. Goel 《Physics letters. A》1973,46(3):221-222
Phonon frequencies for copper have been obtained by extending the work of Yuenand Varshni to include the electron-ion interaction term of de Launay's model. The results thus obtained show a better agreement with the experimental data. 相似文献
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The phonon spectra of unstrained and strained quasiperiodic semiconductor superlattices (QSSL) have been calculated using
one-dimensional linear chain model. We consider two types of quasiperiodic systems, namely cantor triadic bar (CTB) and Fibonacci
sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatch of about 7%. The calculations
have been made using transfer matrix method and also with and without the inclusion of strain. We present the results on phonon
spectra of two component CTB and two as well as three component FS semiconductor superlattices (SSL), thickness and order
dependence on LO mode of GaAs, effect of strain on LO frequency of GaAs. The calculated results show that the strain generated
due to lattice mismatch reduces significantly the magnitudes of the confined optical phonon frequency of GaAs. 相似文献
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Phonon dispersion relations for Sc and Y are calculated along [0001] and [010] symmetry directions using Animalu transition metal model potential. 相似文献
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Conclusion The experimentally measured phonon dispersion relation for niobium is very complex. This complexity may be due to the incomplete electronicd shells which make an important contribution to very large cohesive energy, and its likely effect on the phonon frequencies. Also the anomalies in the dispersion curves may be due to the departure of the Fermi surface from sphericity. In the present study none of the above effects is included explicitly and so theory fails to achieve exact agreement with the experimental data. Finally, we would like to put a concluding remark that an appropriate microscopic treatment given tod electron could explain the phonon dispersion curves of transition metal like niobium.One of the authors (ARJ) would like to express his appreciation to Professor M. K. Agarwal (Head of the Department) for his support and encouragement to carry out this work. Thanks are also due to Sardar Patel University for providing computer facilities. 相似文献
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《Solid State Communications》2002,121(9-10):471-474
We present the phonon dispersion relations of single-wall carbon nanotubes calculated within a force-constants approach. By using the full symmetry group of the tubes, we are able to calculate the dispersion relations for any chirality starting from one single carbon atom. We find an overbending in the highest optical branch between 6 and 12 cm−1 independent of the tube diameter. The order of the high-energy modes at the Γ-point differs from the results derived from simple zone folding. The splitting between the two Raman active optical modes with A1 symmetry at the Γ-point of chiral tubes is ≈4 cm−1 for typical diameters; it increases with decreasing tube diameter. 相似文献
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Rasmita Sahoo Rashmi Ranjan Mishra 《Journal of Experimental and Theoretical Physics》2012,114(5):805-809
The phonon dispersion of graphene is derived by using a simple mass spring model and considering up to the first, second, third, and fourth nearest-neighbor interactions. The results obtained from different nearest-neighbor interactions are compared and it is shown that the k 2 dependence for the out-of-plane transverse acoustic mode obtained in other sophisticated methods as well as experiment occurs only after including the fourth nearest-neighbor interaction. 相似文献
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The phonon dispersion curves for aluminium arsenide and antimonide have been investigated by using a deformation bond approximation
model. The results obtained from this model are compared with the experimental values wherever it is available. Since there
is no complete experimental phonon dispersion curves for AlAs, we could not compare our calculated results, but the results
of AlSb have been compared with the inelastic neutron scattering measurements at 15 K. However, we compare the phonon frequencies
of AlAs and AlSb at critical points of the Brillouin zone obtained by our calculations and Raman spectroscopy measurements.
This model predicts the phonon modes satisfactorily in all the symmetry directions of the Brillouin zone (BZ). The spectrum
has similar features as observed in other III–V compound semiconductors. 相似文献
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W. Press D.E. Cox J.D. Axe G. Shirane J. Harada Y. Fujii S. Hoshino 《Solid State Communications》1975,16(12):1365-1369
Phonon dispersion curves in DC1 at 109 K have been determined. Values of the zero-sound elastic constants C11 = (6.29±0.23), C12 = (3.95±0.22) and C44 = (2.47±0.12) × 1010 dyn cm? re obtained from fitting the data to a harmonic Born-von-Kármán model. This implies a deviation from the Cauchy relation δ = ?0.38±0.08. 相似文献