Materials Literature
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We report here evidence for the first paraferroelectric transition observed in a pure molecular solid (without H bonds); we present results from x-ray diffraction, calorimetric and dielectric measurements, and direct optical observation of domain-wall displacement under an applied electric field.
By using LEED and workfunction measurements it has been found that a previously reported c(2*2) structure for Cs on W(100) was due to a small amount of H accumulated on the surface at the beginning of Cs deposition. These H atoms, in the presence of Cs, form patches of c(2*2).
PrAlO 3 has the cubic perovskite structure at high temperatures but is trigonally distorted at room temperature. At about 200 K it undergoes a first-order phase transition to an orthogonal phase, and there is a further phase transition to a triclinic phase at about 150 K. The authors have studied this system by Raman…
An anomaly in the electrical resistivity is observed in the vicinity of the order-disorder transition in an alloy of composition near ${\mathrm{Fe}}_{3}$Al, which is of the form predicted by Suezaki and Mori for antiferromagnets and, hence, order-disorder systems. The anomaly is qualitatively different from the "ferro…
A full spherical retarding-field energy analyser with three grids was made to measure the total secondary electron yield σ, the backscattering coefficient η, and the secondary electron spectrum N(E) as a function of angle of incidence and primary energy in UHV. The instrumental effects of the grid meshes in the measur…
Abstract The synthesis of 2‐oxa‐6‐aza‐adamantane ( 21 ) and several of its derivatives ( 13–20 , 22 , 23 , 25–34 , 37 , and 38 ) was achieved starting from the 9‐azabicyclo[3.3.1]nona‐2,6‐ dienes 2 , and 3 , and 9‐oxabicyclo[3.3.1]nona‐2,6‐diene ( 1 ).
Abstract Acenaphthylene, C12H8, occurs in space group Pbam (or Pba2) at room temperatures (23 °C) with a = 7.705 (5), b = 7.865 (5), c = 14.071 (5) Å and Z = 4, and is disordered. At about 130 K it undergoes a reversible transition to space group P21 nm with a = 7.588 (13), b = 7.549 (10), c = 27.822 (2) Å and Z = 8 (…
Single crystals of synthetic quartz, plastically deformed at atmospheric pressure and at high temperatures, have been examined in the electron microscope at 100 and 200 kV respectively. Tangles of dislocations are revealed in specimens compressed at temperatures below 800°C. Above this temperature, the dislocations pr…
Values for the ionization energies of the neutral actinides have been derived by utilizing interpolated spectral properties of these atoms. The results in electron volts are Ac: 5.17(12); Th: 6.08(12); Pa: 5.89(12); U: 6.05(7); Np: 6.20(12); Pu: 6.06(2); Am: 5.993(10); Cm: 6.09(2); Bk: 6.30(9); Cf: 6.41(10); Es: 6.52(…
The effect of uniaxial stress on the first-order Raman spectra of the cubic crystals, Ca${\mathrm{F}}_{2}$, Ba${\mathrm{F}}_{2}$, and ${\mathrm{Bi}}_{12}$Ge${\mathrm{O}}_{20}$ is studied at $\ensuremath{\sim}15$ \ifmmode^\circ\else\textdegree\fi{}K using a quantitative-stress cryostat. Both Ca${\mathrm{F}}_{2}$ and Ba…
The polarized light scattering spectrum from a dilute solution of spherical macromolecules is customarily interpreted on the basis of independent particle diffusion. However, it is known that diffusion in such a system is governed by a many particle diffusion equation with cross-diffusion coefficients Dij that depend…
We have observed the EPR spectra of As acceptors in both natural Mo${\mathrm{S}}_{2}$ crystals ($2H$ polytype) and in synthetic Mo${\mathrm{S}}_{2}$ crystals ($3R$ polytype). The $g$ values of the resonance signals show that the As acceptors are associated with a band that has ${d}_{{z}^{2}}$ orbital character. Energy…
Luminescence studies are reported on compounds M(IV)X2P: M is Si, Ge, Sn, Pb; X is F, Cl, Br, I, OH, benzoate; P is etioporphyrin or octaethylporphin. (One tetraphenylporphin is reported for comparison.) We find fluorescence yields 2 × 10−1 ≥slant φf ≥slant 2 × 10−4; phosphorescence yields 7 × 10−2 ≥slant φp ≥slant 3…
X-ray photoelectron spectra (XPS) of the valence bands of crystalline and amorphous As, Sb, and Bi have been measured. The results are compared with band-structure calculations for the crystalline materials. A splitting, $\ensuremath{\Delta}E$, of the "$s$-like" peak for the crystalline phase disappears in the amorpho…
The reaction kinetics of U + 3/2 H2⇄UH3 was studied with fine powders on an ultrahigh-vacuum microbalance. The kinetics were found to be first order with respect to uranium for the hydriding reaction and nearly zero order with respect to uranium hydride for dehydriding. A new reaction mechanism is proposed to account…
The polarized Stokes and anti-Stokes Raman spectrum of amorphous ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ has been measured at several temperatures in the range 20-448 \ifmmode^\circ\else\textdegree\fi{}K with a He-Ne laser, and at room temperature with a c.w. dye laser. Using the Shuker-Gammon data-reduction method, the…
The principle of a new electrochromic display based on an oxidation-reduction reaction of an organic compound of the viologen family is described. The result is a display having a built-in memory, high contrast, a low switching voltage, and a low mean power consumption.
The resonance aspect of chemical bonding is extended to solids with particular emphasis on its consequences for structural and vibrational properties. It is shown, for example, that the square of the infrared effective charge is proportional to the high-frequency dielectric constant in resonance-bonded systems. The IV…
Measurements of the magnetic susceptibility, magnetic moment and specific heat of holmium phosphate, HoPO 4 , show that there is a magnetic phase transition to an antiferromagnetic state at a Neel temperature of 1.39 K. The measurements indicate that the g value of the Ho 3+ ion is highly anisotropic with g c =16.0, g…
Surface-state transitions on ordered silicon (100)2\ifmmode\times\else\texttimes\fi{}1 and (111)7\ifmmode\times\else\texttimes\fi{}7 surfaces have been observed by electron energy-loss spectroscopy. The surface transitions were identified by comparing the clean ordered surfaces with clean disordered surfaces, and with…