Splitting of Wyckoff positions (orbits)

摘要: A crystal structure is composed of one or more sets atoms where the each set are symmetrically equivalent under a space group (‘regular system atoms’ ‘orbit atoms’). For characterization it sufficient to specify atom (each orbit) by coordinates its centre. Relations between structures in chemistry continuous phase transitions manifest themselves (G)-subgroup (H) relations: H < G. Atoms which G may become non-equivalent subgroup H, i.e., ‘the orbit split’. The splitting same for all orbits Wyckoff position but be different positions. In this paper, possible ways and conditions analyzed. Relevant factors are: index group-subgroup relation G-H, order point G, site-symmetry groups and, lesser degree, H. Also kind plays role. most restricted if normal expressed an equation illustrated examples.