avec
    0.0000000000000000    5.1306064620899088    5.1306064620899088
    5.1306064620899088    0.0000000000000000    5.1306064620899088
    5.1306064620899088    5.1306064620899088    0.0000000000000000
atoms
 1
 'Si.in'
 2
  0.0000000000000000  0.0000000000000000  0.0000000000000000
  0.2500000000000000  0.2500000000000000  0.2500000000000000