Materials Literature
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The authors show that phason- and amplitudon-like vibrations can be obtained in one-dimensional incommensurate systems with harmonic interactions between first neighbours only. This is achieved provided a realistic modulation of the force constants is used. The incommensurate systems are approximated by commensurate o…
Strong evidence for the formation of a bound magnetic polaron in $n$-${\mathrm{Cd}}_{0.90}$${\mathrm{Mn}}_{0.10}$Se has been obtained from time-resolved experiments by picosecond laser spectroscopy. In particular, time-varying Stokes shifts associated with a neutral donor bound exciton have been measured to follow the…
The anisotropy of thermal expansion of ZnSiP2, is investigated within 20 to 300 K. For the stronger SiP bond a smaller expansion coefficient and a higher temperature of transition to negative thermal expansion is found than for the weaker ZnP bond. Therefore, similar relations exist between the expansion coefficient…
A simple, thermodynamic model of intercalated graphite which allows for variation of in-plane intercalant density, and takes explicit account of volume variation, is presented. Assuming random occupation of intercalant atoms pressure-temperature-concentration phase diagrams are calculated. The model is capable of expl…
Effects of the lattice dispersion upon anharmonic decay of near-zone-boundary LA phonons in Ge are studied by making reference to the two-phonon density of states in the [100] and [111] directions. As the wave vector approaches Brillouin-zone boundaries, the two-phonon density of states increases more rapidly than ${\…
Using water-in-oil emulsion samples to avoid, for the most part, heterogeneous nucleation, the crystallization of ice from a series of aqueous LiCl solutions has been studied isothermally, using differential calorimetry to monitor the process through the release of the heat of crystallization. The classical form of th…
An x-ray photoemission spectrum of a newly found allotrope of solid selenium, rhombohedral Se containing only ${\mathrm{Se}}_{6}$ ring molecules, has been presented, and compared with those of monoclinic, trigonal, and amorphous forms. The most remarkable points in the density of states of rhombohedral Se are (1) the…
The static and dynamic behavior of the Frederiks transition for twist of a uniform planar nematic sample in an external magnetic field has been studied by monitoring the associated conoscopic figure. In particular, the decay of this figure after the field has been switched off is considered in detail in order to obtai…
We report the polarized Raman spectra of vitreous Ge $^{16}\mathrm{O}_{2}$, Ge $^{18}\mathrm{O}_{2}$, $^{70}\mathrm{Ge}$${\mathrm{O}}_{2}$, and $^{74}\mathrm{Ge}$${\mathrm{O}}_{2}$. This yields the $^{16}\mathrm{O}$\ensuremath{\rightarrow}$^{18}\mathrm{O}$ and $^{70}\mathrm{Ge}$\ensuremath{\rightarrow}$^{74}\mathrm{Ge…
The electronic structures of sodium metasilicate (${\mathrm{Na}}_{2}$Si${\mathrm{O}}_{3}$) and the $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ phases of sodium disilicate (${\mathrm{Na}}_{2}$${\mathrm{Si}}_{2}$${\mathrm{O}}_{5}$) are calculated from first principles by the method of linear combination of atomic orb…
We have measured and interpreted the Raman spectra of bulk $\mathrm{Ge}{({\mathrm{S}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x})}_{2}$ glasses for compositions in the range $0\ensuremath{\le}x\ensuremath{\le}0.25$, both at low power levels and at sufficiently high power levels to induce thermally reversible (at $T\ensuremat…
The density of states for thermal vibrations on a fractal is calculated with careful attention paid to the normalization condition. It is found that at the crossover between Debye-type excitations (long wavelength) and "fracton" excitations (short-length scale) the density of states is discontinuous. The size of the d…
Spontaneous photoluminescence (PL) spectra of Cu-doped and undoped $\ensuremath{\epsilon}$-GaSe have been investigated in the temperature range from 80 to 300 K and at low laser-excitation intensity ($P$) from ${10}^{\ensuremath{-}3}$ to 10 W ${\mathrm{cm}}^{\ensuremath{-}2}$. The main modification of the spectra in d…
The magnetic and structural properties of rapidly quenched FePr(BSi) alloys are presented. The samples are usually magnetically soft in the as-quenched state. However, large coercive fields in the range of 5–20 kOe are developed upon heating the samples to a temperature around 700 °C. The best properties have been obt…
In this paper we discuss the properties of optical elements fabricated by holographically recording an ultrahigh spatial-frequency pattern in a photoresist mask followed by reactive ion etching to transfer this pattern into the surface of a quartz substrate. Such optical elements are environmentally durable, potential…
A versatile method for determination of the optical constants is described that can be applied to a variety of coating materials. It is based on the use of an optical thin film synthesis program to adjust the constants of dispersion equations until a good fit is obtained between measured and calculated spectral transm…
An approximate calculation of the total energy of a transition metal as a function of volume and ionic configuration at constant volume obtained by extending the nearly-free-electron theory of the simple metals to include the effects of transition-metal $d$ bands provides a qualitative first-principles prediction of t…
A relationship between the isobaric, isothermal and isochoric lattice Gruneisen parameters has been examined and analysed for several polymers. Relationships between the various parameters describing the thermo-acoustic and nonlinear properties of polymers are developed and their relations with thermo-acoustic data es…
The theory of the transverse magnetophonon effect is developed for inversion layers in semiconducting heterostructures in the presence of a quantising magnetic field perpendicular to the interface. It is assumed that the electrons move in quasi-two-dimensional sub-bands, and that the optic phonons and the polar electr…
The room-temperature triboluminescent spectra of single crystals of CaF 2 :1% Tb, CaF 2 :1% Dy, CaF 2 :1% Sm and CaF 2 :1% Eu have been recorded using a high-gain image intensifier spectrograph. The spectra, obtained as the crystals were cut with a diamond-impregnated circular saw, show significantly more structure th…