A Method of the Determination of Lattice Constants from Single-Crystal X-ray Photographs

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Abstract
A graphical extrapolation method from single-crystal X-ray photographs was used by Farquhar and Lipson to determine accurate lattice constants of an orthorhombic crystal. An extension of the above method to the case using shorter wavelength radiations such as MoKα is discussed. The difficulties due to the use of such radiations,i.e.low intensities of the Bragg reflections at high angles and a high background, are obviated with the help of a simple attachment to an ordinary single crystal oscillation camera. This technique is also useful for longer wavelength radiations such as CuKα. The application is made to an orthorhombic crystal, sodium nickel double fluoride NaNiF3. The present method will be particularly effective for the crystal with small lattice constants and/or with low symmetry. The method is compared with that using a back-reflection Weissenberg goniometer.