Improvement of high-angle double-crystal X-ray diffractometry (HADOX) for measuring temperature dependence of lattice constants. I. Theory

X-ray diffraction methods for determining accurate temperature dependence of lattice constants are discussed; it is suggested that HADOX is best for general use. The accuracy and precision of the method are examined in full detail in terms of sensitivity, resolution and systematic and accidental errors. The examination is mostly given in comparison with the Bond method. An overall accuracy of a lattice-constant change of one part in 10⁷ can be attained, provided due consideration is given to reducing the errors; the main systematic errors limiting the accuracy are those in the temperature of crystals and in the orientation of crystals or crystal holders. To obtain the accuracy mentioned above, the basic suggestions for changes to a prototype apparatus are presented.