code: import numpy as np
  
  atoms_to_save = np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 15, 18])
  
  u_cdl = np.load("u_cdl.npy")
  v_cdl = np.load("v_cdl.npy")
  
  np.save("u_cdl_modified.npy", u_cdl[atoms_to_save])
  np.save("v_cdl_modified.npy", v_cdl[atoms_to_save])
  
apis: numpy.array numpy.load numpy.save