insufficient memory to allocate a new array

[Gileadc]

Dear all molpro users and devs! 

I am trying to run the following input file (shown below) but I run into this error: 

 "Insufficient memory to allocate a new array of length 3635668608 8-byte words"

I am already allocating a lot of memory to for the calculation (12GW), and I am not sure what exactly I am doing wrong...

1) is my active space too large? I wanted my active space to include the molecular orbitals that are made by 3p-3p (2 sigma states and 4 pi states), 4s-4s (2 sigmas), and 3d-3d (2 sigmas, 4 pis and 4 deltas), have I specified the active space correctly? 

2) am I not allocating enough memory? do I need to allocate even more for the calculation? does it make sense that this calculation uses about 100 gigs of RAM? how can I tell how much memory a calculation needs before I allocate the memory?

best regards and thanks in advance

Gilead

the input file:

***,K2
geometry={K1;K2,K1,r}
basis=cc-pVDZ

r = 10
hf

dr=0.5
i = 1
do r=8,20,dr

{MCSCF;
Closed,4,1,1,0,4,1,1,0;
Occ,9,3,3,2,9,3,3,2;
wf,38,1,0;state,8;
wf,38,4,0;state,8;
}

{MRCI;
wf,38,1,0;ref,4;state,8;
}

do j=1,6,1
e(6*(i-1)+j) = energy(j)
enddo

rr(i)=r
i = i + 1
enddo

{table,e
save,K2_e_MRCI.txt}

{table,rr
save,K2_r_MRCI.txt}
---

[Hans-Joachim Werner]

your casscf is simply too big (14 electrons in 22 orbitals):

Number of closed-shell orbitals: 12 ( 4 1 1 0 4 1 1 0 )
Number of active orbitals: 22 ( 5 2 2 2 5 2 2 2 )
Number of external orbitals: 20 ( 4 3 3 0 4 3 3 0 )

State symmetry 1

Number of active electrons: 14 Spin symmetry=Singlet Space symmetry=1
Number of states: 8
Number of CSFs: 653353848 (3635668608 determinants, 29085255936 intermediate states)
…

Best regards
Joachim
---
Prof. Dr. Hans-Joachim Werner
Institut für Theoretische Chemie
Universität Stuttgart
Pfaffenwaldring 55
70569 Stuttgart, Germany
e-mail: wer...@theochem.uni-stuttgart.de

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[Gileadc]

thanks for the response!

and yeah, that's what I thought, how would you suggest decreasing the active space without decreasing the accuracy of the calculation too much?

and do you have any other suggestions?

thanks in advance

Gilead