Space group notation and related point groups

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SUMMARY

The discussion centers on space group #55, Pbam, and its relationship with point group mmm. It confirms that Pbam is indeed consistent with point group mmm, despite the presence of two glide planes and one mirror, which may lead to confusion regarding its symmetry elements. The user also notes that while Pbam can generate a crystal with symmetry C2h, it does not support D2h symmetry. The notation "D^9_2h mmm" indicates the symmetry properties of the space group rather than directly correlating to the point group.

PREREQUISITES
  • Understanding of space group notation in crystallography
  • Familiarity with point groups and their symmetry elements
  • Knowledge of crystal structures, specifically orthorhombic systems
  • Basic concepts of glide planes and mirror planes in symmetry
NEXT STEPS
  • Research the implications of space group symmetry on crystal properties
  • Explore the relationship between space groups and point groups in crystallography
  • Study the classification of orthorhombic crystal systems
  • Investigate energy band structures in solids and their relation to symmetry
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Crystallographers, materials scientists, and researchers studying solid-state physics who require a deeper understanding of space group and point group relationships.

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I'm looking at the space group #55, Pbam.

In the top of the file (see below) it has listed:

Pbam D^9_2h mmm Orthorhombic

Is this saying that Pbam is consistent with point group mmm?

It does not have three mirrors, it has two glide plane and one mirror.

If I look at the space group, I see that it can create a crystal that has C2h but not D2h.

Am I missing something? Is the "D^9_2h mmm" in the table telling me something other than the point group -- if so, what?

http://it.iucr.org/Ab/ch7o1v0001/sgtable7o1o055.pdf


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