As mentioned in the introduction to this chapter, the entire SCF part of the DALTON code is direct, including all derivative two-electron integrals, and all the way up to the cubic response function. To perform a direct calculation, all that is required is to add the keyword .DIRECT in the general input section, as indicated in the following input example for the calculation of nuclear shieldings in a direct fashion:
**DALTON INPUT .RUN PROPERTIES .DIRECT **WAVE FUNCTIONS .HF **PROPERTIES .SHIELD *END OF INPUT
By default the two-electron integrals will be screened, and a integral
threshold of 
is the default threshold for whether an
integral will be calculated or not. This can be changed with the
keywords .IFTHRS
and .ICEDIF
.