Pyrrhotite superstructures; Part II, A TEM study of 4C and 5C structures

2C triclinic, 4C and 5C hexagonal superstructures of pyrrhotite have been found in specimens from Nagyborzsony, Hungary. SAED (Selected Area Electron Diffraction) patterns taken from [100] and [110] directions of the hexagonal NiAs-type subcell are compared with the intensity values calculated for the theoretical structures presented in Part I of this work (Posfai & Dodony, 1990). The 2C phase is found to have a 10203040 stacking sequence of iron layers whereas the 10203000 structure is confirmed for the 4C phase. Two types of basic 5C structure occur in the specimens; one with a 1020103040, the other with a 1020030400 sequence. TEM images are used to observe random stacking phenomena.