共查询到20条相似文献,搜索用时 15 毫秒
1.
Lattice parameters, thermal expansion coefficients and Grüneisen parameters of silicon are determined by an X-Ray diffraction method in the temperature range of 180–40 K without the use of liquid gases. Thermal expansion of silicon becomes negative below 120 K which is discussed in terms of its lattice vibrations and crystal structure. 相似文献
2.
I. A. Gospodarev A. V. Eremenko K. V. Kravchenko A. F. Sirenko V. A. Sirenko E. S. Syrkin S. B. Feodosyev Yu. A. Shabakaeva 《Physics of the Solid State》2013,55(4):898-904
The characteristic features of thermal expansion of bulk samples of niobium diselenide have been determined experimentally and analyzed theoretically. The manifestation of the so-called membrane effect in this compound due to the significant difference in the temperature dependences of the mean-square amplitudes of atomic displacements in the parallel and perpendicular directions toward the layers has been investigated. 相似文献
3.
V. V. Novikov D. V. Avdashchenko N. V. Mitroshenkov A. V. Matovnikov S. L. Bud’ko 《Physics of the Solid State》2014,56(10):2069-2076
Thermal characteristics of the phonon and magnon subsystems of icosahedral borides RB66 (R = Gd, Tb, Dy, Ho, Eu, or Lu) have been studied based on the obtained experimental data on the thermal expansion of the borides and the earlier results on their heat capacity in the range of 2–300 K. The contribution to the expansion of borides containing paramagnetic R 3+ ions, which is characteristic of transition to the spin-glass state, has been revealed. The phonon spectrum moments of RB66 compounds and the Grüneisen parameters have been calculated. 相似文献
4.
The thermal expansion of the superconductor La3S4 has been investigated on a single crystal by a capacitive method between 1.6 and 14 K. The relative length change shows a well pronounced second order phase transformation near 8.05 K, which is caused by the superconducting transition. From the calculated linear thermal expansion coefficient we determine the pressure coefficient of the transition temperature and of the thermodynamic critical field as well as the thermodynamic critical field itself. Furthermore we estimate the electronic, phononic and total Grüneisen parameters. These parameters have been used to discuss on the basis of the McMillan equation the reason for the increase of the transition temperature under pressure. 相似文献
5.
The thermal expansion coefficient of cadmium fluoride crystals has been measured over the temperature range of 300 to 1070 K. The data fit well to measurements done by other authors in the range 80–300 K. At temperatures above 1070 K the thermal expansion coefficient shows an anomalous behaviour which has been attributed to the formation of cadmium oxide on the surface of the sample. 相似文献
6.
The origins of the anomalous (negative) thermal expansion of high-temperature superconductors (HTSCs) and of the anomalously strong effect of a magnetic field on the thermal expansion coefficient at low temperatures are discussed. A physical model is proposed based on the stabilizing influence of a charge density wave (CDW) arising in the oxygen sublattice in addition to the antiferromagnetic and spin-Peierls ordering in the copper ion sublattice of an HTSC compound. The effects of temperature, magnetic field, and doping on the interaction of such a CDW with the ionic subsystem of an HTSC compound are studied. The conclusions derived from the model are in agreement with experimental data. 相似文献
7.
Arun S. Wagh 《Journal of Physics and Chemistry of Solids》1981,42(3):185-191
Recent investigations of X-ray diffraction and electron micrograph studies reveal high density clusters separated by density deficient regions (voids) in amorphous materials. The low temperature specific heat and the thermal conductivity anomalies are explained on the basis of such a structure for amorphous materials. It is a generalisation of Debye's theory applied to most of the amorphous solids in the temperature range from 0 to 10 K. The anharmonic effects lead to the observed temperature dependence of the sound velocity. The thermal conductivity between 0 and 2 K is due to thermal diffusion, the plateau observed between 2 and 20 K is a consequence of the decrease in thermal conductivity due to three phonon processes compensated by intercluster diffusion, while beyond this range it is due to excitations within a cluster limited by the size of a cluster. Further the model predicts the coefficient of expansion about 100 times that found in the corresponding crystalline solids. An experimental verification of this result can be a good test for the model. 相似文献
8.
采用真空热压技术在高真空和温度为523K的情况下,通过不同压力将直径平均大约为45nm的Cu纳米粉末压制成纳米结构Cu固体材料,将X射线衍射、扫描电镜与物性测试仪(PPMS)相结合,研究了低温下纳米结构Cu固体材料的比热容随温度和材料密度的变化.研究结果表明:低温比热容随着纳米结构Cu固体材料密度的降低而升高;纳米结构Cu固体材料的低温比热容大于粗晶Cu,其增加率在10K左右达到极大.基于缺陷的热振动效应,探讨了这些现象的物理机理. 相似文献
9.
We derive iterated Mayer expansions for classical gases and establish recursive bounds which control their convergence. These bounds are useful for gases with two body forces which are strong and possibly attractive at distances that are short compared to their range. Our procedure is based on splitting the potential into pieces of decreasing strength and increasing range. This may be called a renormalization group treatment of a classical gas. We apply our results to Yukawa lattice gas models and obtain convergence of series expansions for the pressure for a range of parameters (temperature, fugacities, range of the interaction) that was inaccessible before. Application to 3-dimensionalU(1) lattice gauge theory (Coulomb gas,Z-ferromagnet) will be made elsewhere.Work supported in part by Deutsche Forschungsgemeinschaft 相似文献
10.
11.
J. Chaussy J. Le G. Gilchrist J.C. Lasjaunias M. Saint-Paul R. Nava 《Journal of Physics and Chemistry of Solids》1979,40(12):1073-1078
The existence of a distribution of low-lying energy levels associated with holes trapped at substitutional aluminium impurities is confirmed by measurements of low temperature specific heat and dielectric loss. A large linearly temperature-dependent contribution to the specific heat is observed at temperatures below 1 K, down to 30 mK. A localization temperature describing the width of the distribution of the energy levels is estimated to vary between 3 and 6 K.
We determined the thermal conductivity down to 30 mK and attribute the decrease below the boundary-scattering value to irradiation damage generally, arguing that it is not attributable to resonant scattering. 相似文献
12.
13.
Anil Kumar 《Physics letters. A》1982,87(8):421-422
Thermal conductivity of YIG can be analysed by using the low temperature phonon- and magnon-conductivities. They are obtained by solving the nonlinear Boltzmann equation as previously done by Kumar. 相似文献
14.
G. Gilat 《Solid State Communications》1977,23(8):567-570
It is shown by arguments of plausibility that when interatomic forces include mainly central two body interactions, then the sign of the thermal expansion coefficient for isotropic solids at low temperature can be negative only for solids that lack symmetry of inversion. It is deduced that for RbBr and RbI, angular three-body forces play an important role in the nearest neighbor interactions. 相似文献
15.
L. A. Kuzik Yu. Ye. Petrov V. A. Yakovlev G. N. Zhizhin F. A. Pudonin P. Grosse V. Offermann 《Zeitschrift für Physik B Condensed Matter》1994,93(2):239-242
Optical and electric properties of superthin niobium films (d=0.15–2.7 nm) deposited on -quartz using radio-frequency sputtering have been studied at room temperature and at low temperature. A periodic thickness dependence of the metal film's optical and DC conductivity was found. The period of such oscillations is of the order of the electron Fermi wavelength in Nb. Thus they are proposed to be due to quantum size effects in the metal film. 相似文献
16.
A dilatometer, using the three terminal capacitance technique, suitable for measurement of linear thermal expansion of solids
in the temperature range 1.3–300 K is described. The dialtometer is designed such that the mounting system for the specimen
does not undergo any significant changes in dimensions when the specimen is heated. The apparatus, therefore, yields in principle
absolute values of α, the coefficient of linear thermal expansion. The performance of the apparatus has been checked by measurements
on copper in the temperature range of 77–300 K. Some preliminary results on the behaviour of α for Y1Ba2Cu3O6.9 compound in the vicinity of superconducting transition temperature,T
c are also described. The system can detect relative changes in length Δl/l
0 of about 10−8. Attempts are being made to improve the sensitivity. 相似文献
17.
Isotope labelling experiments have established that the adsorption of O2 on the W(110) plane at 20 K leads first to the formation of a dissociated atomic layer. A weakly bound molecular species, α-O2, forms only when the atomic layer is essentially complete (O/W = 0.6). The desorption of α-O2 was found to be first order with an activation energy of and a frequency factor γ = 3 × 109 s?1. The activation energy is shown to be less than the enthalpy of desorption and the meaning of this result is discussed. 相似文献
18.
A theory of the thermal expansion of the plane and (11n) stepped surfaces of fcc crystals is presented. The temperature dependent relaxations arise from cubic anharmonic terms in the crystal potential energy. We show that the thermal expansion depends on the positions of the atoms with respect to the steps and is greatest for the atom of the upper corner. The knowledge of these new atomic positions at each temperature allows us to calculate new atomic force constants and then new vibrational properties at this temperature. The application is made for a Ni crystal for which we give the corrections, due to the thermal expansion, on the mean square displacements of stepped surface atoms. The variation with temperature of the optical modes due to a light monolayer is also presented. 相似文献
19.
P. Varanasi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,30(6):481-490
Measurements of spectral transmittance in the v4-fundamental band of 12CH4 have been performed at low temperatures using a Fourier transform spectrometer with apodized spectral resolution of 0.06 cm-1. With applications to lines formed in the atmospheres of Titan and Earth in mind, N2 has been used as the broadening gas. Comparisons of observed and computed spectral transmittances on a line-by-line basis have yielded line strengths, N2-broadened half-widths and their variation with temperature. Best agreement between measured and computed spectra was obtained when the absolute intensity of the band was taken as 128 cm-2-atm-1 at 296 K. Line widths were found to vary as Tn with n = -1.0 for lines of the F-species and 0.63 for the A-species. Our measured line widths are considerably larger than those used in the AFGL compilation. 相似文献
20.
B. Riccó 《Solid State Communications》1977,22(5):331-333
The Fermi energy of niobium diselenide is calculated and the result is used to compute the wave-vector dependent susceptibility χ(q). This is found to have a fairly narrow peak at a wave-vector in very good agreement with that of the periodic lattice distortion developed by the solid at low temperature and such a peak can be seen to arise from good nesting of the Fermi surface. 相似文献