MOLPRO

14 INTEGRATION 83
< cuto f f > is the exponential parameter of the cutoff-function.
When < ncentres > is lower than zero, only the integrals are calculated and saved in the record
1490.1. Otherwise, the h 0 matrix (records 1200.1 and 1210.1) and the two-electron-integrals
(record 1300.1) will be modified.
CPP,ADD,< f actor >;
With this variant, previously calculated matrix elements of the polarization matrix can be added
with the variable factor < f actor > (default: < f actor > = 1) to the h 0 -matrix as well as to the
two-electron-integrals. In particular, CPP,ADD,-1.; can be used to retrieve the integrals without
the polarization contribution.
CPP,SET,< f cpp >;
normally not necessary but may be used to tell MOLPRO after a restart, with what factor the
polarization integrals are effective at the moment. Currently the CPP integrals are restricted to
basis functions up to and including angular momentum 4, i.e. g functions.
13.2 Example for ECP/CPP
***,Na2
! Potential curve of the Na2 molecule
! using 1-ve ECP + CPP
gprint,basis,orbitals;
rvec=[2.9,3.0,3.1,3.2,3.3] ang
do i=1,#rvec
rNa2=rvec(i)
geometry={na;na,na,rNa2}
basis={
ecp,na,ecp10sdf; ! ecp input
s,na,even,8,3,.5; ! basis input
p,na,even,6,3,.2;
d,na,.12,.03;
}
cpp,init,1;
! CPP input
na,1,.9947,,,.62;
hf;
ehf(i)=energy
{cisd;core;}
eci(i)=energy
enddo
table,rvec,ehf,eci
---
http://www.molpro.net/info/current/examples/na2_ecp_cpp.com
14 INTEGRATION
Before starting any energy calculations, the geometry and basis set must be defined in GEOMETRY
and BASIS blocks, respectively. By default, two electron integrals are evaluated once and stored
on disk. This behaviour may be overridden by using the input command gdirect (see section
14.2) to force evaluation of integrals on the fly. MOLPRO checks if the one-and two-electron
integrals are available for the current basis set and geometry, automatically computing them if
necessary. The program also recognizes automatically if only the nuclear charges have been
changed, as is the case in counterpoise calculations. In this case, the two-electron integrals are
not recomputed.