qp2/content/page/try.md

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You can try Quantum Package in the terminal below. To configure the terminal for your favorite text editor, set the EDITOR environment variable:

export EDITOR=vim

Here is an example of a few commands you can run to get the Full-CI energy of the HCN molecule.

First create a file named hcn.xyz containing the xyz coordinates.

$ cat << EOF > hcn.xyz
3
HCN molecule
C    0.0    0.0    0.0
H    0.0    0.0    1.064
N    0.0    0.0    -1.156
EOF

Create the EZFIO database as follows:

qp create_ezfio -b 6-31g hcn.xyz -o hcn

Run a Hartree-Fock calculation:

qp run SCF | tee scf.out

The MOs are saved in the EZFIO database. Now freeze the core electrons:

qp set_frozen_core

And run the CIPSI calculation in the valence full CI space:

qp run fci | tee fci.out

That’s it!