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。
The basal-plane shear stress-strain behavior of small, highly anisotropic-annealed natural graphite single crystals was studied at room temperature. A static uniaxial-shear stress was applied directly along the basal plane with a minimum of normal force, incorporating a technique to detect translations down to ∼40 Å.…
Transition-metal oxides and sulfides can be insulators, semiconductors, or metals, or undergo metal-nonmetal transitions. The experimental situation in these materials is briefly reviewed. Pure Bloch-Wilson theory predicts that many of the insulators should be metallic, so this class cannot be explained in terms of pu…
Various anomalous optical, magnetic, and transport phenomena have been found in Eu-chalcogenide alloys. Anomalous optical properties are explained by the magnetic exciton in which a hole in the $4f$ conduction band and an electron (for optically active magnetic exciton) in the $5d$ conduction band make a bound state.…
A study of the possibility of the existence of stacking faults in b.c.c. crystals on {110} and {112} planes has been performed, representing the lattice by a central force interaction between atoms. The same study was also carried out for {111} planes in f.c.c. crystals. The results for the f.c.c. lattice are in full…
Abstract The general conformations of a system of three linked peptide units are studied, and it is found that there are three types of conformations which contain NH…O hydrogen bonding between the first and the third units. One of them is part of a 3 10 ‐helix, while the other two arc nonhelical. The two nonhelical c…
It is proposed that the dominant mechanism for electrical conduction in NiO and similar materials is by means of holes in the oxygen $2p$ band. A band-structure diagram which takes into account the primarily localized $3d$ states is suggested.
The one-exciton, one-magnon system is treated for a suitable antiferromagnetic insulator, Mn${\mathrm{F}}_{2}$. Zone-edge excitons and magnons are found to interact quite strongly. Bound states are found to exist under favorable circumstances. The line shapes of magnon sidebands of excitonic transitions are modified.…
We have extended earlier work on the Raman spectrum of quartz to both higher and lower temperatures (6-900\ifmmode^\circ\else\textdegree\fi{}K), and find evidence for the assignment of features in the 130- to ${200\ensuremath{-}\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$ region as second order. Anomalies in the temperatu…
It was recently suggested that the metal-nonmetal transition which occurs in ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ at \ensuremath{\simeq}120\ifmmode^\circ\else\textdegree\fi{}K may be of the Mott-Wigner type. Present results on the effects of pressure on the transition temperature and the conductivity of the low-tempe…
Ferroelectric properties in gadolinium molybdate are shown to originate from a new mechanism completely different from that in conventional ferroelectric materials. In this crystal the spontaneous polarization results from an elastic instability which gives rise to a spontaneous strain in the original piezoelectric pa…
With the help of the correlation-function formula given by McLennan, an expression for the viscosity tensor is obtained within the Hartree-Fock approximation using the cubic anharmonic momentum-flux operator. In the Debye approximation for phonons and with a simple expression for relaxation time, solutions are obtaine…
The weak-field magnetoresistance coefficients have been measured in niobium-doped SrTi${\mathrm{O}}_{3}$ at 4.2, 77, and 120\ifmmode^\circ\else\textdegree\fi{}K. The results at 77 and 120\ifmmode^\circ\else\textdegree\fi{}K are consistent with a conduction-band structure consisting of minima along the $〈100〉$ reciproc…
The optical density between 2400 and 7000 Å of the vapor in equilibrium with Si–Te samples containing between 10 and 100 at.% Te was measured for sample temperatures between 500° and 940°C. The partial pressures of Te2(g), pTe2, were obtained from the optical densities at 4357, 5000, and/or 5500 Å, where SiTe(g) does…
The frequencies and symmetries of the even-parity lattice vibrations of BaClF, BaBrF, and SrClF are determined by means of polarized Raman scattering from oriented single crystals. The polarizations and frequencies of the vibrations are interpreted in terms of symmetry coordinates.
The band structures of the lead salts PbS, PbSe, and PbTe have been studied by electro-optic methods. Electroabsorption and electroreflectance measurements have been made over the energy ranges 0.25 to 0.65 eV and 0.6 to 5.5 eV, respectively, using an electrolyte to produce electric fields at the surface of these mate…
Lattice vibrations in elemental crystals can possess a first-order electric moment, and thus exhibit reststrahlen (symmetry-allowed one-phonon infrared absorption), by the mechanism of displacement-induced charge redistribution (dynamic charge). By a group-theoretical investigation of the relation between symmetry and…
Abstract A new theoretical analysis is made of the elastic constants of crystalline native cellulose. Primary interatomic forces are considered in the calculation of the Young modulus in the chain direction, where we retrieve a result identical to that of Treloar. Hydrogen bonds provide the main mechanism for determin…
Measurements of the magnetization and differential susceptibility of GdAl${\mathrm{O}}_{3}$ have been made in pulsed magnetic fields in the temperature range 1.3-100\ifmmode^\circ\else\textdegree\fi{}K. It is found that GdAl${\mathrm{O}}_{3}$ is a uniaxial antiferromagnet with the easy axis of magnetization along the…
An electron-paramagnetic-resonance study of rare-earth impurities in II-VI compounds has been made. Isolated trivalent rare-earth ions are found to be substitutional for the metal ion in the zinc-blende crystals. Spectra from trivalent ions both at the isolated substitutional site and incorporated in additional unknow…
A comprehensive study of the properties of "source-free" wave fields (i.e., diffracted wave fields expressible by plane-wave expansions containing only homogeneous waves) is summarized. The theorems proved in the study are stated. A new series mode expansion for "source-free" wave fields in included.