# CISD calculation

**URL:** <https://discuss.pennylane.ai/t/cisd-calculation/4414>\
**Category:** PennyLane Help\
**Created:** [April 9, 2024, 6:56pm UTC](https://discuss.pennylane.ai/t/cisd-calculation/4414 "2024-04-09T18:56:21Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![souzateixeira](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/souzateixeira/32/2020_2.png) [@souzateixeira](https://discuss.pennylane.ai/u/souzateixeira)\
**Post date:** [April 9, 2024, 6:56pm UTC](https://discuss.pennylane.ai/t/cisd-calculation/4414/1 "2024-04-09T18:56:21Z")

</div>

Hello,  
I tried to run the following commands for 3 molecules: H3+, CH5+, and C7H5O4.

```auto
myhf = scf.RHF(mol).run()
myci = ci.CISD(myhf).run()
wf_cisd = import_state(myci, tol=1e-1)

```

It works for H3+ and CH5+ but fails to the last one

```auto
---------------------------------------------------------------------------
IndexError Traceback (most recent call last)
Cell In [8], line 1
----> 1 wf_cisd = import_state(myci, tol=1e-1)

File ~/.local/lib/python3.9/site-packages/pennylane/qchem/convert.py:630, in import_state(solver, tol)
    628 wf = _wfdict_to_statevector(wf_dict, len(solver[0][0]))
    629 else:
--> 630 wf = _wfdict_to_statevector(wf_dict, solver.mol.nao)
    632 return wf

File ~/.local/lib/python3.9/site-packages/pennylane/qchem/convert.py:657, in _wfdict_to_statevector(wf_dict, norbs)
    655 bin_b += "0" * (norbs - len(bin_b))
    656 bin_ab = "".join(i + j for i, j in zip(bin_a, bin_b))
--> 657 statevector[int(bin_ab, 2)] += coeff
    659 statevector = statevector / np.sqrt(np.sum(statevector**2))
    661 return statevector

IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices

```

Can someone help me?  
Attached is the file created to run  
[cisd.py](https://discuss.pennylane.ai/uploads/short-url/guCOXSSOB6evi0GUYS1cxu80ojA.py) (2.2 KB)

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [April 9, 2024, 11:39pm UTC](https://discuss.pennylane.ai/t/cisd-calculation/4414/2 "2024-04-09T23:39:17Z")

</div>

Hi @souzateixeira, that last molecule is very very big. Unless you’re running this on a very large cluster you’re going to run out of memory. Unfortunately I don’t think any of the usual tricks will be enough to run that molecule. I’m sorry I don’t have better news for you.