29.8.2 The MULTP directive

The MULTP directive turns on the multipole approximations for distant pairs, as described in Ref. [8]. Further options can be given as described above for the LOCAL directive.

LOCAL,MULTP,options

is equivalent to

MULTP,options

The level of the multipole approximation can be chosen using option DSTMLT (default 3) ( 1 means dipole approximation, 2 quadrupole approximation and so on).

The multipole approximation reduces the computational cost of LMP2 calculations for very large molecules, but leads to some additional errors, see Ref. [8]. It is normally not recommended to be used in coupled-cluster calculations and should never be used for computing intermolecular forces. It can also not be used in geometry optimizations or gradient calculations.