Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
High-temperature phase transitions in KH 2 PO 4 near 110°C and 180°Chave been studied by X-ray diffraction. The extinction rule observed at 123°C is the same as that in the room-temperature phase. It is concluded that on heating through 187°C crystal system changes from tetragonal to monoclinic whose space group is P…
By use of a capacitance method, the thermal expansions of NaNO 2 ( T C =163.9°C, T N =165.2°C) along the a -, b - and c -axes were measured from -180°C to 240°C with the accuracy of 1×10 -6 cm in Δ l . Anomalies associated with the phase transitions were observed over the wide temperature range 100 to 200°C. The therm…
The problem of electronic energy transport is solids in discussed. A model system of two molecules interacting with a lattice of phonons is considered. The spectral line shapes and energy transport are treated in various limiting cases, and the connection between these two phenomena is discussed.
A dynamical Landau theory is proposed to describe the coupled motion of phonons and charge-density waves (CDW) near the CDW instability in transition-metal dichalcogenides. The dynamic structure factor is shown to exhibit a Kohn anomaly and a diverging central mode.
Considerable information about transport and recombination properties of amorphous ${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$ has been obtained from studies of steady-state and transient photoconductivity, dark conductivity, and thermopower in the temperature range from 200 to 350\ifmmode^\circ\else\textdegree\fi{}K: (i)…
We present a method for calculating the one- and two-phonon law $S(Q,\ensuremath{\omega})$ for models of amorphous solids. The calculation is considerably simplified by explicitly performing the necessary orientation averages. We illustrate use of the method by calculating the one-phonon scattering from long-wavelengt…
It has been found that in NH 4 LiSO 4 another transition point 186.5°C exists in addition to the already known one 10°C and this substance is ferroelectric between these two transition points. Anomalies of dielectric constant at the transition points are very small as compared with those of proper ferroelectrics. The…
Simultaneous measurements of the thermal conductivity and specific heat of copper-aluminum (2, 5, 8, and 12 at.%) alloy crystals have been done by the temperature-wave method at 1.4–7.5 K. Specimens containing dislocations of medium (10 10 cm -2 ) and high (10 12 cm -2 ) densities were used. In the case of crystals of…
The one-phonon scattering law for a disordered harmonic system is related to a frequency-dependent displacement-displacement correlation function. We suggest a means of investigating this correlation function by means of a suitable transformation of inelastic neutron scattering data for such systems.
Electrical, magnetic, and thermal properties of $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{S}}_{2}$ and $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{Se}}_{2}$ doped with cations (Ti, Zr, Hf, V, Nb), $1T\ensuremath{-}\frac{{\mathrm{Nb}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{S}}_{2}}{\mathrm{Se}}$, and $1T\ens…
An approximate relativistic treatment of the differential cross section for Compton scattering against bound electron states is discussed. A simple relationship between the cross section and the Compton profile is found. On contrast to previous work this relationship is valid for all scattering angles.
The very-low-frequency Raman scattering from vitreous silica was measured for frequency shifts $\ensuremath{\omega}$ as small as 4 ${\mathrm{cm}}^{\ensuremath{-}1}$. The data were compared with present theories on disorder-induced sacttering; for $\ensuremath{\omega}<20$ ${\mathrm{cm}}^{\ensuremath{-}1}$ an excess…
A new method for measuring absolute electron-impact differential cross sections (DCS) for elastic scattering in gases is described. The technique uses a well-defined crossed-beam scattering geometry in which the relative target densities of an unknown and a secondary standard gas are accurately determined by a calibra…
Magnetic-susceptibility and EPR measurements are reported which provide the first unambiguous evidence for a spin-Peierls transition in a system of linear one-dimensional antiferromagnetic Heisenberg chains. The material studied is TTFCu${\mathrm{S}}_{4}$${\mathrm{C}}_{4}$${(\mathrm{C}{\mathrm{F}}_{3})}_{4}$ (TFF stan…
We have used the technique of static field induced second harmonic generation in liquids to determine the second order hyperpolarizability β, and the third order hyperpolarizability γ, for a wide range of conjugated and nonconjugated organic molecules. The adequacy of the Onsager local field formulation was tested as…
The Raman spectra of some binary alkali silicate glasses and crystals have been measured and the results interpreted. The glasses are of composition M2O⋅xSiO2, 1⩽x⩽4 and M = Li, Na, K. There is a strong resemblance between glassy and crystalline spectra which is consistent with a considerable amount of structural diso…
The energy distributions of electrons transmitted through thin free films of Be, Al and Ge with initial energies of E 0 =0.5-4.0 keV have been investigated with a spherical retarding-field analyser. The most probable (E m /E 0 ) and mean (E/E 0 ) energies as a function of the penetration depth x depend on the Z of the…
Liquid-crystal twisted nematic structures can be made with twist angles other than the conventional 90 degrees . It is shown that theoretically the transmission of such a structure when placed between two polarizers aligned parallel and perpendicular to the respective surface molecular directors is given by T=(1+u 2 )…
Logarithmic anomalies in the temperature-dependent resistivity of a series of amorphous alloys have been measured and shown to be nonmagnetic in origin. We associate these anomalies with the noncrystalline structure.
Electron energy loss measurements have been made up to 40 eV on specimens of several members of the mica group and quartz. By means of a Kramers-Kronig analysis the dielectric functions epsilon 1 and epsilon 2 have been deduced from the energy loss function. The excitations observed in mica and quartz are discussed wi…