The electron distribution in the phases CoAl and NiAl

Abstract

X-ray intensity measurements for powders of CoAl and NiAl, using Ag Kα radiation, were placed on an absolute scale by direct measurement of the power in the incident beam. Effects due to preferred orientation, surface roughness and extinction were shown to be negligible and measurements using Co Kα radiation confirmed the absence of effects which vary with wavelength. The experimental structure factors were shown to agree with those calculated from theoretical scattering factors for the ground state free atoms, if suitable temperature factors are used, with the exception of the experimental 〈200〉 structure factors which are a few per cent low. The main structural feature corresponding to the differences between calculated and experimental structure factors is an additional charge density between the atoms along the contact directions; this is illustrated by Fourier syntheses corresponding to the outer electron distributions.