Wrong structure from spacegroup I4/mmm

[vladimirovpv]

System

• Pymatgen version: pymatgen (4.3.0)
• Python version: Python 2.7.6
• OS version: Ubuntu 14.04.4 LTS

  Summary

• The following code should generate structure of Be12Ti. For both spacegroup "I4/mmm" or its number "139" (as in example below) the code generate POSCAR file with 8 Ti and 8 Be atoms, which is obviously wrong as the ratio of Be/Ti should be 12.
• The input data for the structure are based on ICSD 616454.

  Example code

import pymatgen as mg                                                                                                                                                              
from pymatgen.analysis.defects.point_defects import Interstitial                                                                                                                   

lat = mg.Lattice.tetragonal(7.35,4.19)                                                                                                                                             
structure = mg.Structure.from_spacegroup("139",lat,["Be","Ti"],
    [[0.25, 0.25, 0.25],
    [0.35, 0.0,  0.0 ],
    [0.28, 0.50, 0.0 ],
    [0.0,  0.0,  0.0 ]])
structure.to(filename="POSCAR")

Error message

no error message, but wrong output to POSCAR

Suggested solution (if any)

• Too many symmetry operations were applied to Ti atoms, while for Be some were missing.

  Files (output POSCAR)

Ti8 Be8
1.0
7.350000 0.000000 0.000000
0.000000 7.350000 0.000000
0.000000 0.000000 4.190000
Be Ti
8 8
direct
0.250000 0.250000 0.250000 Be
0.750000 0.750000 0.750000 Be
0.750000 0.750000 0.250000 Be
0.750000 0.250000 0.250000 Be
0.750000 0.250000 0.750000 Be
0.250000 0.250000 0.750000 Be
0.250000 0.750000 0.750000 Be
0.250000 0.750000 0.250000 Be
0.350000 0.000000 0.000000 Ti
0.650000 0.000000 0.000000 Ti
0.850000 0.500000 0.500000 Ti
0.000000 0.350000 0.000000 Ti
0.150000 0.500000 0.500000 Ti
0.000000 0.650000 0.000000 Ti
0.500000 0.850000 0.500000 Ti
0.500000 0.150000 0.500000 Ti

[shyuep]

Your input is wrong. The ["Be", "Ti"] should be ["Be", "Ti", "Ti", "Ti"] I think.

[vladimirovpv]

Thank you! Now it works. The correct input should be other way round: ["Be","Be","Be","Ti"].