Open-shell BCCD calculations

[Benoît Oswald Stanislas BRAÏDA]

Dear sir,


I've tried (unsuccesfully !) to compute brueckner coupled-cluster 
open-shell calculations. My calculation end with an "ERROR EXIT" due 
to "UNREASONABLE NORM". I don't now why : rccsd and uccsd calculation 
on this molecule ended normally.

I've tried different options (UHF or RHF wave function, RBCCD(T) or 
UBCCD(T)) on Molpro 1998 (version : 98.1) and MOLPRO 2000 (version : 
2000.1), without succes.


The end is invariably :


>
> UNREASONABLE NORM. CALCULATION STOPPED
>
> Norm of t1 vector:     29.35082813      S-energy:    -3.32071501 
>T1 diagnostic:  1.56393809
> Norm of t2 vector:    340.71454444      P-energy:    -0.67620331
>
> Spin contamination <S**2-Sz**2-Sz>     0.00000000


My input file is :


> memory,22,m
> gprint,orbital=5
>
> basis=vdz
>
>  HN1 = 1.02500 angs
>  HN2 = 1.03000000 angs
>  A1 = 115.000000000 degree
>  A2 = 90. degree
>  NN = 5. angs
>
> geometry={y;
> zmat
> N1
> N2,N1,NN
> H1,N1,HN1,N2,A1
> H2,N1,HN1,N2,A1,H1,120.
> H3,N1,HN1,N2,A1,H1,-120.
> H4,N2,HN2,N1,A2,H1,180.
> H5,N2,HN2,N1,A2,H4,120.
> H6,N2,HN2,N1,A2,H4,-120.
> endz
> }
>
> int
> rhf
>  start,2140.2
>  occ,8,2
>  wf,19,1,1
>  natorb,ci
>  e_hf(i)=energy
>
> rccsd
> rbccd(t)



 Thanks for your attention and I am looking forward to hear
your reply.



Benoît BRAIDA

Laboratoire chimie physique
Groupe de chimie théorique
Université Paris-Sud, Batiment 490
91405 ORSAY CEDEX
Tél : 01-69-15-61-91
Fax : 01-69-15-44-47