With the exception of perturbative triples corrections, all methods implemented in MOLPRO can be performed in integral-direct mode, i.e., without storage of the two-electron integrals on disk. Naturally, this takes longer than conventional calculations, since the integrals are recomputed whenever needed. The integral-direct mode is activated by giving the gdirect directive before the first energy calculation, e.g.,
***,formaldehyde print,basis,orbitals !this is optional: print the basis set and the !occupied orbitals angstrom geometry= !define the nuclear coordinates C O , C , rco H1 , C , rch , O , hco H2 , C , rch , O , hco , H1 , 180
rco=1.182 Ang rch=1.102 Ang hco=122.1789 Degree
gdirect !integral-direct calculation basis=vdz !Select basis set hf !Perform HF calculation mp2 !Perform MP2 calculation