def rvdw_change(rotamer_library, radius_vdw_info, start_index, end_index):
    """
    Change all radius vanderwals 0 to 0.5
    from the rotamer's library file
  """
    with open(rotamer_library, 'r') as f:
        lines = f.readlines()
        for i, new_line in enumerate(radius_vdw_info):
            lines[start_index + i] = (
                '{0:>5} {1:>8} {2:>8} {3:>10} {4:>8} {5:>8} {6:>13} {7:>13}\n'
                .format(*new_line))
    with open(rotamer_library, 'w') as f:
        f.write(''.join(lines))
