openbabel / openbabel/openbabel

Unit cell dimensions might not follow lattice type

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Description

For CIF file (http://www.crystallography.net/cod/1000032.html) with cell parameters:

_space_group_IT_number           167
_symmetry_cell_setting           trigonal
_symmetry_space_group_name_Hall  '-R 3 2"c'
_symmetry_space_group_name_H-M   'R -3 c :H'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            6
_cell_length_a                   4.76050(5)
_cell_length_b                   4.76050(5)
_cell_length_c                   12.9956(2)

Resulting PDB cell parameters are:
CRYST1 4.761 4.760 12.996 90.00 90.00 120.00 H -3 c 1

For this type of lattice, a MUST be equal to b.

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  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by examining the linked CIF record and comparing its cell parameters with the resulting CRYST1 record shown in the issue. Trace the CIF-to-PDB conversion path and verify that the converted lattice preserves the required equality of a and b for this lattice type; done means the output reflects that constraint and the case is covered by a regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
data
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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