Acta Phys. -Chim. Sin. ›› 1989, Vol. 5 ›› Issue (01): 107-109.doi: 10.3866/PKU.WHXB19890123

• Note • Previous Articles    

How to Specify Origin and Enantiamorph with General Reflections

Hou Yong-Kang;Fu Heng   

  1. Institute of Chemistry, Academia Sinica
  • Received:1987-05-11 Revised:1988-04-16 Published:1989-02-15
  • Contact: Hou Yong-Kang

Abstract: For non-centrosymmetric crystal structures, it is usually uses as many specila refletions as possible to define origin and enantiamorph. But in some cases, special reflections may be not enough or may be not in good quality to specify origin and enantiamorph so questions about specifying origin and enantiamorph with general reflections are discussed in this paper. Origin definition reflections of any space groups are differentiated into absolute freedoms and relative freedoms so that the problem of assigning values to the general refection phases for specifying origin is able to be solved. The concept of freedom is also used in enantiamorph specification. Two cases about enantiamorph specification relection related to or not related to origin definition refections are disecussed respectively. In both cases enantiamorph specification can be realized through two steps: (1) Chosing the signs of a certain number of structurral invariants (2) On the basis of step one, making restrictins to the amplitudes and phase signs of the invariant's component reflections.