qiskit-documentation/docs/api/qiskit/0.26/qiskit.chemistry.drivers.ps...

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---
title: psi4d (v0.26)
description: API reference for qiskit.chemistry.drivers.psi4d in qiskit v0.26
in_page_toc_min_heading_level: 2
python_api_type: module
python_api_name: qiskit.chemistry.drivers.psi4d
---
<span id="module-qiskit.chemistry.drivers.psi4d" />
<span id="qiskit-chemistry-drivers-psi4d" />
# PSI4 Installation
[PSI4](http://www.psicode.org/) is an open-source program for computational chemistry. In order for Qiskits chemistry module to interface PSI4, i.e. execute PSI4 to extract the electronic structure information necessary for the computation of the input to the quantum algorithm, PSI4 must be [installed](http://www.psicode.org/downloads.html) and discoverable on the system where Qiskits chemistry module is also installed.
Therefore, once PSI4 has been installed, the psi4 executable must be reachable via the system environment path. For example, on macOS, this can be achieved by adding the following section to the .bash\_profile file in the users home directory:
```sh
# PSI4
alias enable_psi4='export PATH=/Users/username/psi4conda/bin:$PATH'
```
where username should be replaced with the users account name. In order for the chemistry module to discover PSI4 at run time, it is then necessary to execute the enable\_psi4 command before launching Qiskit.