# MRCI thresholds or contractions

Fabio Mariotti mariotti at mpi-muelheim.mpg.de
Fri Oct 31 14:26:02 GMT 2003

```

Dear Molpro users,

I have the following problem:
I'm running an ACPF calculation on HF molecule
close to dissociation:
namely i'm computing 4 points. Here the distancies
and ACPF energies:

VRDFH        EACPF
4.95   -100.0478137
5.00   -100.0478125
5.05   -100.0477949
5.10   -100.0477939

as you can see from 5.00 to 5.05 there is a "jump"

After a while I realised that the main difference
in the two points (5.00/5.05) is the number of
contractions in the MRCI/ACPF part.

So for the 5.00 geometry I have:

Total number of contracted configurations:         2588
Total number of uncontracted configurations:       8642

While for 5.05 geometry:

Total number of contracted configurations:         2368
Total number of uncontracted configurations:       8642

For reference here is my current test input:
===========================================================
***,nh3                     !A title
!
print,ref,pspace;
gprint,basis,orbitals=8;
!
rdfh=1.00000000;
geometry={angstrom;
F;
H, 1, rdfh;
}
!
gthresh,oneint=1.0E-14,twoint=1.0E-14,zero=1.0E-14,preface=1.0E-20;
!
basis=aug-cc-pVDZ;
!
i=0;
do ist=4.90,5.1,0.05;
!
i=i+1;
rdfh=ist;
vrdfh(i)=rdfh;
!
hf;accu,20;core;
!
casscf;
acpf;
eacpf(i)=energy;
!
enddo;
!
text,START TABLE FOR get_molpro_table.pl;
table,vrdfh,eacpf;
plot,FILE=plot.dat;
text,END TABLE FOR get_molpro_table.pl;
!
---
!
===========================================================

I've been playing around with all the cutoff/thresholds I know

Does anybody knows how I can solve this problem?

The CAS before the MRCI looks identical (beside the small
changes due to the different geometries).

Which other parameters the number of contractions can
depend on?

(I'm using molpro 2002.3 and 2002.6)