def METHOD_NAME():
    """
    Set up Si primitive cell
    Si
       5.431
         0.0000000000000000    0.5000000000000000    0.5000000000000000
         0.5000000000000000    0.0000000000000000    0.5000000000000000
         0.5000000000000000    0.5000000000000000    0.0000000000000000
    Si
       2
    Direct
      0.8750000000000000  0.8750000000000000  0.8750000000000000
      0.1250000000000000  0.1250000000000000  0.1250000000000000
    """
    structure_data = DataFactory('core.structure')
    alat = 5.431
    lattice = np.array([[.5, 0, .5], [.5, .5, 0], [0, .5, .5]]) * alat
    structure = structure_data(cell=lattice)
    for pos_direct in ([0.875, 0.875, 0.875], [0.125, 0.125, 0.125]):
        pos_cartesian = np.dot(pos_direct, lattice)
        structure.append_atom(position=pos_cartesian, symbols='Si')
    return structure