text: #!/usr/bin/env python
  import numpy as np
  import numpy.linalg as linalg
  import ase.io
  import ase.build.bulk as asebulk
  import ase_module
  
  symbol = 'Ni'
  structure = 'diamond'
  a = 3.508
  fname_out = '{}_{}_cubic.vasp'.format(symbol,structure)
  
  # create the orthogonal unit cell
  cell = ase_module.make_structure(symbol,
          structure,
          a,
          is_cubic=True,
          is_orthorhombic=False)
  
  # create the nonorthgonal unit cell
  try:
      ase_module.write_ase_structure_as_poscar(
          ase_cell = cell, 
          fname_out=fname_out)
  except FileExistsError:
      print("the file exists")
  