Materials Literature
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The thermal conductivity $K$ and the thermoelectric power $Q$ of single-crystal samples of rutile were measured from 2 to 300\ifmmode^\circ\else\textdegree\fi{}K. Pure, niobium-doped, vacuum-reduced, and hydrogen-reduced specimens were investigated. The thermal conductivity of the pure crystals is similar to that usua…
The anharmonic contributions to the energy, specific heat, frequency-wave-vector dispersion relations and damping of phonons in a crystal have been studied using the recent technique of thermodynamic Green's functions based on field-theoretic methods. General expressions for these quantities have been deduced. It has…
A diagram technique suitable for calculating equilibrium classical statistical properties of solid dielectrics is developed. The method is applied to the temperature-dependent dielectric susceptibility and vibration spectrum of an anharmonic crystal. The techniques of "diagram summation" and "frequency renormalization…
The magnetic properties of Fe${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2${\mathrm{H}}_{2}$O have been investigated by means of single-crystal magnetic susceptibility, high-field magnetization, and proton nuclear-magnetic-resonance (nmr) measurements. A transition to an antiferromagnetic state is obs…
The FMR (ferromagnetic-resonance) measurements were performed in single crystals of silicon-iron, nickel-iron, nickel, and hcp cobalt in the frequency region 8-140 Gc/sec at room temperature. The samples, in the form of thin discs, were statically magnetized parallel to the plane of the disc. Their thickness was at le…
Measurements of the absorption between 0.3 and 1.0 mm have been made on NaCl, KCl, KBr, KI, NaI, and LiF between room temperature and 15\ifmmode^\circ\else\textdegree\fi{}K. Present theory explains the absorption in this region as arising from "vertical" transitions from one phonon state to another with the same wave…
The spin-wave thermal conductivity of ferromagnetic insulators with magnetic scattering is investigated. The role of magnon-magnon interactions is clarified. The magnetoelastic coupling is treated by the Green-function technique.
Group-theoretical selection rules are given for two-phonon infrared absorption and Raman scattering processes in crystals having the rocksalt structure. In common with the diamond structure, two-phonon overtones are infrared inactive. The selection rules for second-order infrared absorption processes in the rocksalt s…
Polarized absorption in the 5D2←7F0 transition and emission in the 5D0→7F2 transition of the Eu3+ ion have been obtained in monoclinic single crystals of the tetrahexylammonium salt of tetrakis diphenyl-propanedionoeuropium (III). Both sets of transitions consist of three lines, two polarizing strongly perpendicular t…
Lamellar compounds of graphite are often, but not always, deeply colored. To study this color, a number of different compounds have been prepared from very thin flakes cleaved from annealed single crystals. The spectral transmission of these samples has been measured between 0.2 μ and either 2.2 μ or, in a few cases,…
Results on dielectric polarization and its variations in strong electric fields are presented for solutions of hexanol-1 in hexane, benzene, 1,4-dioxane, and triethylamine. A method for calculating the dipole moments of multimers and complexes on the basis of experimental results is proposed. Also, the concentrations…
Powder x-ray-diffraction studies on tellurium up to 150 kbar show only two structural transitions at 40 and 70 kbar in agreement with Bridgman's work. The structure of the 40–70-kbar phase is unsolved. Above 70 kbar, it is proposed that tellurium is isomorphous with β-polonium and is rhombohedral with a=3.002±15 Å, α=…
Normal frequencies of crystalline polymethylene have been calculated for various phase differences along the c axis of the crystal. Intermolecular hydrogen—hydrogen force constants have been evaluated from the splitting of the spectroscopically active modes. The results of the calculations explain almost satisfactoril…
Abstract Morphology and kinetics of the spherulite crystallization has been studied for d,l ‐poly‐(propylene oxide) ( d,l ‐PPO) (M̄ n = 135,000) and l ‐PPO (M̄ n = 10,300). Both polymers have similar physical characteristics except that d,l ‐PPO normally gives non‐ringed spherulites whereas l ‐PPO exhibits the ringed…
The principal absorption bands induced by irradiation at liquid-helium temperature with x rays in CsBr crystals are the complex $F$ band and two overlapping $V$ bands at 435 and 497 m\ensuremath{\mu}. In view of the dichroic properties of these $V$ bands, the most obvious model seems to be a ${\mathrm{Br}}_{2}^{\ensur…
The thermoelectric power of Cu-Al and Cu-Si alloys has been determined from 4.2 to 320\ifmmode^\circ\else\textdegree\fi{}K. Assuming that the thermopower is separable into diffusion and phonon-drag components, the change in phonon-drag thermopower $\ensuremath{\Delta}{S}_{g}$ is determined for Cu+0.77 at.% Al and Cu+1…
The electronic band structure of ordered beta brass (${\ensuremath{\beta}}^{\ensuremath{'}}$ CuZn) has been calculated from first principles by the Green's-function technique. Two slightly different crystal potentials of the muffin-tin type have been tested, both based on free-atom Hartree-Fock wave functions. Each po…
The experimental results of phonon-drag thermoelectric power of $n$-InSb are analyzed to obtain information about electron-phonon and phonon-phonon interactions. We find that for temperatures greater than 6\ifmmode^\circ\else\textdegree\fi{}K, the piezoelectric mode of electron scattering is negligible as compared to…
The data of Allen and Gobeli on photoemissive yields from partially cesiated surfaces of several semiconductors with photon energies between 2 and 6 eV are analyzed in detail. The results are shown to be consistent with direct transitions in energy-band models obtained from semiempirical pseudopotentials based on inte…
An elementary analysis is given of the conditions for phase transformations of the first and second orders, in the molecular-field approximation. The analysis may be relevant to some ferroelectric, Jahn-Teller, order-disorder, and singlet-triplet transitions. On the assumptions of our two-level model, no transition ca…