If CUTOFF=6 is used, then GNORM=20 is recommended. Once the geometry is optimized using GNORM=20, the CUTOFF should be increased (9 is a good value for general use) or removed, and GNORM reduced to, e.g., GNORM=10.
For the rare occasions when finer control is needed, use CUTOF1 and CUTOF2.
In MOZYME calculations, the cutoff distance for polarization functions is set by CUTOF1=n.nn. Beyond that distance, electrostatic interactions are considered only as point charges. At distances less than that given by CUTOF1, electrostatic interactions are represented by a point-charge and three polarization functions. Default: For systems of less than 30 atoms, CUTOF1 is 1000 Ångstroms; for systems of 30 or more atoms, CUTOF1 is 30 Ångstroms.
In MOZYME calculations, the cutoff distance for two-electron two center and one-electron two center integrals is set by CUTOF2=n.nn. Below that distance, the interaction between two atoms is represented by the exact NDDO approximation. Above that distance, one-electron integrals that depend on the overlap are ignored, and two-electron integrals are simplified. Instead of using all 100 two-electron integrals between two heavy atoms, only seven are used. These represent the terms <ss|ss>, <ss|sx>, <ss|sy>, <ss|sz>, <sx|ss>, <sy|ss>, and <sz|ss>. At still greater distances, beyond CUTOF1, only the <ss|ss> term is used. Default: For systems of less than 30 atoms, CUTOF2 is 1000 Ångstroms; for systems of 30 or more atoms, CUTOF2 is 12 Ångstroms.