message: Added default setting for positions in LMBTR that is dientical to SOAP and ACSF.
diff: @@ -316,7 +316,9 @@ class LMBTR(MBTR):
  indices_k3 = []
  new_pos_k3 = []
  new_atomic_numbers_k3 = []
  + n_atoms = len(system)
  if positions is not None:
  + n_loc = len(positions)
  # Check validity of position definitions and create final cartesian
  # position list
  @@ -356,6 +358,14 @@ class LMBTR(MBTR):
  "Create method requires the argument 'positions', a "
  "list of atom indices and/or positions."
  )
  + # If positions are not supplied, it is assumed that each atom is used
  + # as a center
  + else:
  + n_loc = n_atoms
  + indices_k2 = np.arange(n_atoms)
  + indices_k3 = np.arange(n_atoms)
  + new_pos_k2 = system.get_positions()
  + new_atomic_numbers_k2 = system.get_atomic_numbers()
  # Calculate the "raw" outputs for each term.
  mbtr = {}
  @@ -403,7 +413,6 @@ class LMBTR(MBTR):
  array /= i_norm
  # Flatten output if requested
  - n_loc = len(positions)
  if self.flatten:
  length = 0
  @@ -682,7 +691,7 @@ class LMBTR(MBTR):
  # Form new indices that include the existing atoms and the newly added
  # ones
  - indices.extend([n_atoms_ext+i for i in range(n_atoms_new)])
  + indices = np.append(indices, [n_atoms_ext+i for i in range(n_atoms_new)])
  k3_list = cmbtr.get_k3_local(
  Z=fin_system.get_atomic_numbers(),
  