psi3 command not found

In this troubleshooting guide we learn how to fix psi3 command not found error message

Introduction

When you run more command in linux terminal / console, you get the following error message

psi3: command not found

or when using sudo you get the following error message

sudo: psi3: command not found

Solutions to psi3: command not found

How To Fix psi3: command not found in Ubuntu / Debian / Kali Linux / Raspbian

In Ubuntu psi3 is provided by psi3 package.

psi3 is:

PSI3 is an ab-initio quantum chemistry program. It is especially designed to accurately compute properties of small to medium molecules using highly correlated techniques.

It can compute energies and gradients for the following methods:

  • Closed shell and general restricted open shell Hartree-Fock (RHF/ROHF) (including analytical hessians for RHF)
  • Closed shell Moeller-Plesset pertubation theory (MP2)
  • Complete active space SCF (CASSCF)
  • Coupled-cluster singles doubles (CCSD)
  • Coupled-cluster singles doubles with pertubative triples (CCSD(T)) (only for unrestricted (UHF) reference wavefunctions)

Additionally, it can compute energies for the following methods:

  • Unrestricted open shell Hartree-Fock (UHF)
  • Closed/open shell Moeller-Plesset pertubation theory (MP2)
  • Closed shell explicitly correlated MP2 theory (MP2-R12) and spin-component scaled MP2 theory (SCS-MP2)
  • Multireference configuration-interaction (MRCI)
  • Coupled-cluster singles doubles with pertubative triples (CCSD(T))
  • Second/third-order approximate coupled-cluster singles doubles (CC2/CC3)
  • Multireference coupled-cluster singles doubles (MRCCSD)
  • Closed shell and general restricted open shell equation-of-motion coupled- cluster singles doubles (EOM-CCSD)

Further features include:

  • Flexible, modular and customizable input format
  • Excited state calculations with the CC2/CC3, EOM-CCSD, CASSCF, MRCI and MRCCSD methods
  • Internal coordinate geometry optimizer
  • Harmonic frequencies calculations
  • One-electron properties like dipole/quadrupole moments, natural orbitals, electrostatic potential, hyperfine coupling constants or spin density
  • Utilization of molecular point-group symmetry to increase efficiency

To fix this problem, we can install more using the command below.

sudo apt-get -y install psi3

This command might take some time to finish depending on your machine internet connection.

You can also use apt command to install psi3.

sudo apt -y install psi3

Or if you have aptitude installed you can use the following command.

sudo aptitude install psi3

Summary

In this tutorial we learn how to fix psi3 command not found error in Ubuntu / Debian / Kali Linux or Raspbian distribution.