1 """Module for building atomic structures"""
   2 
   3 from ASE import ListOfAtoms, Atom
   4 
   5 
   6 def BCC100(symbol, a, layers, h):
   7     """Build a bcc(100) surface
   8 
   9     symbol: chmical symbol ('H', 'Li', ...)
  10     a     : lattice constant
  11     layers: number of layers
  12     h     : height of unit cell"""
  13 
  14     # Distance between layers:
  15     z = a / 2
  16 
  17     assert h > layers * z, 'unit cell too small for ' + str(layers) + ' layers'
  18     
  19     # Start with an empty ListOfAtoms object:
  20     atoms = ListOfAtoms([], periodic=True)
  21     
  22     # Fill in the atoms using scaled coordinates:
  23     for n in range(layers):
  24         position = [0.5 * (n % 2),
  25                     0.5 * (n % 2),
  26                     -n * z / h]
  27         atoms.append(Atom(symbol, position))
  28         
  29     # The unit cell is orthorhombic:
  30     atoms.SetUnitCell((a, a, h))
  31     # The unit cell could also have been set like this:
  32     # atoms.SetUnitCell([(a, 0, 0),
  33     #                    (0, a, 0),
  34     #                    (0, 0, h)])
  35     return atoms
  36 
  37 
  38 if __name__ == '__main__':
  39     bcc = BCC100('Al', 3.25, 4, 20.0)
  40     from ASE.Visualization.RasMol import RasMol
  41     p = RasMol(bcc, (4, 4, 2))
  42     raw_input('Press [enter] to finish. ')