Published online by Cambridge University Press: 06 March 2019
A commercial powder diffractometer linked to an IBM 1800 time sharing computer is used for the precision determination of lattice parameters on single crystals with Bond's method of measuring the angle between two diffracting positions of the crystal, symmetric to the incident x—ray beam. A remote x-ray tube and collimator allows a high angle Bragg reflection to be measured easily in these two positions with only one detector. After scanning the two diffraction line profiles, the peak positions and the lattice parameter are determined on line by the computer. Several methods for determining the peak position are discussed. Using these techniques, the lattice parameter of silicon has been determined on two crystals of high purity and perfection to a0 = 5.43093 ± 0.00002 Å and a0 = 5.43095 ± 0.00002 Å at 25°C. These values are in excellent agreement with Bond's result, a0 = 5.430935 ± 0.000019 Å, and they differ slightly from the value a0 = 5.43074 ± 0.00017 Å, the mean value of, lattice parameters measured on silicon powder in 16 laboratories under the I.U.Cr. precision lattice parameter project.