# ITensorChemistry Electron to Fermion Mutual Information Maps

**URL:** https://itensor.discourse.group/t/itensorchemistry-electron-to-fermion-mutual-information-maps/1260
**Category:** ITensor Julia Questions
**Tags:** mps, dmrg, fermions
**Created:** [November 3, 2023, 10:33am UTC](https://itensor.discourse.group/t/itensorchemistry-electron-to-fermion-mutual-information-maps/1260 "2023-11-03T10:33:01Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![FTarocco](https://avatars.discourse-cdn.com/v4/letter/f/85f322/32.png) [@FTarocco](https://itensor.discourse.group/u/FTarocco)
#### Post date: [November 3, 2023, 10:33am UTC](https://itensor.discourse.group/t/itensorchemistry-electron-to-fermion-mutual-information-maps/1260/1 "2023-11-03T10:33:02Z")

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Hi,

I’m using the method that we discussed in [this topic](http

s://itensor.discourse.group/t/mutual-information-matrix/1167) to compute the Mutual Information Maps.

I’ve checked the result obtained by the snippet of code that I’ve implemented, with the GS obtained by ED of the Heisenberg Model Hamiltonian for a 3x3 lattice.  
The results are the same.

Now, I’ve moved on the part on which I am more interested, which is Molecular Hamiltonian.  
Using ITensorChemistry, I’ve computed some GS of some molecules (H2, H2O, etc) and using the Mutual Information snippet I’ve obtained the Mutual Information Maps.

 ![H2O_sto-3g](https://global.discourse-cdn.com/free1/uploads/itensor/original/1X/6e845b163a6d0010af21e8d97f1a3b2ce30c2602.png)

This are obtained with a MPS in which the sites are Electron, but I would like to have fermionic sites, so instead of N spin orbitals, I’d like to have the MPS as 2N spatial orbitals.

I was looking at the source code and found that I can pass the sitetype = “Fermion”/“Qubit” and obtained the desired MPS as fermions.  
Computing the MI map, I’ll obtain the following map

 ![H2O_sto-3g_fermio](https://global.discourse-cdn.com/free1/uploads/itensor/original/1X/35d5de3ad4d601bf5015bee9b19d150a1d4298ab.png)

So, the question is In **the mapping from Electron to Fermion, the final position of spatial orbitals will be up,down,up,down,… ,** right? Or, Am I misunderstanding this part of the code?

> <https://github.com/mtfishman/ITensorChemistry.jl/blob/main/src/molecular_orbital_hamiltonian.jl#L118-L120>

Is there a way to place all the up spatial orbitals in the first N sites and down orbitals in the second group of N sites?

Best,  
Fabio.