SIMULATION OF X-RAY POWDER DIFFRACTION PATTERNS FOR DISORDERED GRAPHITE-LIKE MATERIALS

S.V.Cherepanova, S.V.Tsybulya

Boreskov Institute of Catalysis, pr.Lavrentieva 5, Novosibirsk, 630090 Russia. E-mail: tsybulya@catalysis.nsk.su

Keywords: microstructure, defects, carbon.

A direct simulation of the X-ray diffraction patterns of quasi- graphitic carbon materials with different structural defects based on the model of an imperfect crystal of the definite size has been performed. The program [1] realized the full profile analysis method [2] has been used. The model of imperfect carbon crystal has been considered as a sequence of biperiodic graphitic layers with defects of the layers displacement and fluctuations in the layers positions (variations in the displacement vectors).

Our calculation revealed that disorder in the layers sequences ABAB... and ABCABC... leads to the change in the relationships between intensities of 10l reflections. Fluctuations in the layers positions affect a broadening of 11l reflections.

The powder diffraction pattern has been calculated for the random sequence of the A,B,C-type layers, excluding appearance of the AA, BB, CC-subsequences. It was shown that this model involving significant variations in the interlayer displacement vectors allows to describe diffraction patterns of a number of filamentary carbon materials with coherently scattering domains about 2-6 nm.

1. Cherepanova S.V., Tsybulya S.V., A new program for full profile analysis of imperfect crystals, 5th European Powder Diffraction Conference, Parma, Italy, May 25-28, 1997, 60.
2. Drits V.A.,Tchoubar C., X-ray Diffraction by Disordered Lamellar Structures, Springer-Verlag Berlin Heidelberg, 1990.