B. L. Averbach

Pair correlations in solid lead near the melting temperature

Abstract The scattering of X-rays by an assemblage of randomly orientated small crystallites is expressed in terms of an average pair correlation function. Fourier transforms of the intensity function are calculated by means of a digital computer program, and these provide data on the nearest neighbor distance, the mean square amplitude of vibration, the near neighbor vibrations and the mean potential function. Experimental results have been obtained for lead at 325°C, just below its melting point. The lattice parameter is 5.013 ± 1.0 A, and the mean square amplitude of vibration, u 2 s , is 0.088 A 2 , corresponding to a Debye temperature of 69°K. The vibrational coupling factors for the first six shells are 0.47, 0.59, 0.68, 0.73, 0.76 and 0.79. The anharmonicity of the vibrations is indicated by the difference between the peak position of the first shell, 3480 A and the mean position, 3.544 A. The mean potential function shows a minimum at the nearest neighbor position of −0.066eV.

X‐Ray Diffractometer for the Study of Liquid Structures

An automatic x‐ray diffractometer for the investigation of liquid structures has been built. The specimen is held in a horizontal position. The x‐ray source and detector rotate in a vertical plane about the center of the specimen face, maintaining equal angles of incidence and diffraction and a constant d(sinθ)/dt. Precise adjustment devices are provided for the parameters of the diffraction geometry and for a crystal monochromator which may be located in either the incident or diffracted beam. A variety of specimen holders may be used, including a high temperature stage which is designed to minimize condensation of vapors evaporating from the specimen.

Determination of X‐ray scattering factors with liquid specimens

Abstract : An analysis is described for obtaining x-ray scattering factors from intensity measurements on liquid specimens. Experimental results for the shape of the scattering factor curves for lead, mercury and tin are compared to Thomas-Fermi-Dirac, Hartree-Fock-Slater, HartreeFock, Hartree (self-consistent field) and relativistic calculations. (Author)

Shorting and Field Corrections in Hall Measurements

A method is given for correcting the measured Hall voltage for shorting by the current contacts and for inhomogeneities in the applied magnetic field. This method is applied to measurements of the Hall coefficient in gold‐silver alloys.

Determination of Small Thermal Expansion Coefficients by a Micrometric Dilatometer Method

A method for the measurement of small thermal expansion coefficients in the vicinity of room temperature is described. The thermal expansion of Invar in the room temperature range may be reduced to zero by the elimination of impurities from the basic 36 Ni, bal. Fe composition.