https://github.com/mosdef-hub/mbuild/blob/7da0c05b848e521d81aa8ad17194cc681a997389/mbuild/formats/lammpsdata.py#L1136 Even though the box has no tilt, this lines makes the modify kspace throw an error, in case the tilt is 0.0 0.0 0.0 this line should be omitted.