37.2 First example

A typical input for SAPT has the following form:

r=5.6
geometry={nosym; he1; he2,he1,r}
basis=avqz

!wf records
ca=2101.2
cb=2102.2

!monomer A
dummy,he2
{hf; save,$ca} sapt;monomerA !monomer B dummy,he1 {hf; start,atdens; save,$cb}
sapt;monomerB

!interaction contributions
sapt;intermol,ca=$ca,cb=$cb


Here the sapt;monomerA/B store some informations about the two monomers which are needed in the subsequent SAPT calculation invoked by sapt;intermol. The individual interaction energy terms are stored (in millihartree) in distinct variables and may be collected in arrays for producing potential energy surfaces. For example the input

geometry={nosym; he1; he2,he1,r}
basis=avtz

!wf records
ca=2101.2
cb=2102.2

!distances
dist=[4.5,5.0,5.5,5.6,6.0,6.5,7.0]

do i=1,#dist
r=dist(i)

!monomer A
dummy,he2
{hf; save,$ca} sapt;monomerA !monomer B dummy,he1 {hf; start,atdens; save,$cb}
sapt;monomerB

!interaction contributions
sapt;intermol,ca=$ca,cb=$cb

elst(i)=E1pol;  exch(i)=E1ex
ind(i)=E2ind;   exind(i)=E2exind
disp(i)=E2disp; exdisp(i)=E2exdisp
etot(i)=E12tot

data,truncate,\$ca
enddo

{table,dist,elst,exch,ind,exind,disp,exdisp,etot
ftyp,d,d,d,d,d,d,d,d,d
plot}


yields the plot

Currently SAPT only accepts single-determinant wave functions for the monomers, i.e. from Hartree-Fock or Kohn-Sham DFT (see next section) calculations. This means that if Hartree-Fock wave functions are used for monomer, the following quantity is obtained (zero in superscript denotes that no intramonomer correlation is accounted for) [1].

No point group symmetry can be exploited in a SAPT calculation.

molpro@molpro.net 2019-03-25