The a dimension of graphite

Abstract

Not an abstract, but rather the main findings... Similar to using the 000l peaks to determine the c lattice parameter, using the hki0 peaks to determine the a lattice parameter gives an error. This is due to the fact that the peak is caused by only 2 dimensional diffraction as discussed in Warren (1941), but even with large crystallites, the reciprocal lattice cylinder from the 2D plane still has some finite width givin a slightly shifted peak. Using an hkil line instead alleviates this problem since that is by necessity caused by the 3D structure and is hence more well defined. Warren gives the relation between the breadth and the expected shift in determined d spacing from a certain peak.