An X-ray diffraction study of silicon carbide structure types [(33)_n34]₃R

Abstract

A comparative study of the calculated relative intensities of 10.l reflections for the five members 21R, 39R, 57R, 75R and 111R of the silicon carbide structure series [(33)_n34]₃R (Zhdanov-Ramsdell notation) has been made. Characteristics of the intensity distribution in the 10.l row line, for the entire series of structures, have been derived, enabling a direct identification of higher members without undergoing tedious intensity calculations. A new polytype 111R has been discovered and is shown to have a structure [(33)₅34]₃. The structure is confirmed by the excellent agreement between observed and calculated relative intensities of diffracted x-rays. The origin and growth of this series of structures is discussed.