text: from vasp import Vasp
  from ase import Atom, Atoms
  import numpy as np
  LC = [2.75, 2.8, 2.85, 2.9, 2.95, 3.0]
  for a in LC:
      atoms = Atoms([Atom('Cu', [0, 0, 0])],
                    cell=0.5 * a * np.array([[ 1.0,  1.0, -1.0],
                                             [-1.0,  1.0,  1.0],
                                             [ 1.0, -1.0,  1.0]]))
      calc = Vasp('bulk/Cu-bcc-{0}'.format(a),
                  xc='PBE',
                  encut=350,
                  kpts=[8, 8, 8],
                  atoms=atoms)
      print(calc.potential_energy)