If you have not already done so, you should take a look at the eT_launch page to get an understanding of how the launch script works.

A Hartree-Fock (HF) calculation is performed by specifying a HF wave function
in the method section of the input file.
Available HF methods are
RHF (`hf`

), UHF (`uhf`

), ROHF (`rohf`

), CUHF (`cuhf`

), and MLHF (`mlhf`

).
E.g., for a RHF calculation we write

```
- method
hf
```

At the HF level, single-point calculation and geometry optimization can be performed.
To select one of them, specify either `ground state`

or `geometry optimization`

in the do section.
E.g., for a single-point calculation

```
- do
ground state
```

A minimal working example for an RHF single-point calculation on water:

```
- do
ground state
- method
hf
- geometry
basis: cc-pVDZ
H 0.86681 0.60144 0.00000
H -0.86681 0.60144 0.00000
O 0.00000 -0.07579 0.00000
```

Note

For open-shell calculations you might want to specify the multiplicity
in the system section. The default multiplicity is `1`

.

Save this as `h2o.inp`

and invoke the launch script.

```
path/to/eT_launch.py h2o.inp
```

After the calculation finished you should find `h2o.out`

and `h2o.timing.out`

in your working directory.
If the calculation exited successfully
(look for `eT terminated successfully!`

at the bottom of the file),
the output file should show iteration information
for the solver converging the Hartree-Fock equations.
The table with the iteration information should end with something like this:

```
...
7 -75.989795840960 0.5997E-05 0.2341E-07
8 -75.989795841698 0.2378E-05 0.7377E-09
9 -75.989795841773 0.2055E-06 0.7489E-10
---------------------------------------------------------------
Convergence criterion met in 9 iterations!
```

Including the solver scf section
in the input allows to specify the settings of the HF calculation,
as e.g. the energy or residual thresholds, in more detail.
You may want to loosen the thresholds for the HF calculation
as the default energy and residual thresholds (\(10^{-7}\))
are chosen to be rather tight.
If you also want to get the molecular orbital coefficients,
the `write orbitals`

keyword has to be specified in this section.

```
- solver scf
energy threshold: 1.0d-4
residual threshold: 1.0d-4
write orbitals
```

The orbital coefficients are written to a separate file which is automatically copied
to the output directory by the launch script.
The orbital coefficient file would be called `h2o.mo_coefficients.out`

in this example.

If you wish to compute Mulliken or Loewdin (or both) population analysis you need to add
the keyword `population analysis:`

in the solver scf and then specify
`mulliken`

, `loewdin`

or `all`

.
The population analysis will be saved in separate files, which in this example would be called
`h2o.Mulliken_population_analysis.out`

and `h2o.Loewdin_population_analysis.out`

where you can
find the atomic charges and reduced orbital charges.

```
- solver scf
population analysis: mulliken
```