The Hautman-Klein Ewald method in DL_POLY_2 permits the user to perform a
real space sum over nearest-neighbour and next-nearest-neighbour cells
(i.e. up to nlatt=2). If the user specifies a larger sum than
this, this error will result.
Action:
The user should respecify the HK control parameters
given in the CONTROL file and set nlatt to a maximum of 2.
(See 4.1.1).