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 Density Functional Theory (DFT) calculation is performed by specifying the keyword dft
in the method section of the input file.
At the moment, only restricted DFT calculations are available (`dft`

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

```
- method
dft
```

The DFT method is defined by specifying the DFT functional. This can be done in the dft functional section of the input file. Please, refer to the available functionals specified in dft functional section E.g., for a hybrid B3LYP calculation we write

```
- dft functional
b3lyp
```

The DFT calculation requires the definition of a molecular grid. A molecular grid is automatically generated by eT. If can also be specified by including the grid info section in the input file. E.g., for a grid with a quadrature of 30th order and a radial threshold set to 1.0E-6 we write:

```
- grid info
radial : 1.0e-6
angular : 30
```

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

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

```
- do
ground state
```

A minimal working example for an hybrid B3LYP RDFT single-point calculation on water:

```
- do
ground state
- method
dft
- dft functional
b3lyp
- geometry
basis: cc-pVDZ
O 0.00000 0.00000 0.11779
H 0.00000 0.75545 -0.47116
H 0.00000 -0.75545 -0.47116
```

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 Density Functional Theory equations.
The table with the iteration information should end with something like this:

```
...
7 -76.420393564026 0.1575E-06 0.2373E-10
8 -76.420393564027 0.2269E-07 0.4832E-12
9 -76.420393564026 0.1009E-08 0.8527E-13
10 -76.420393564027 0.5342E-10 0.8527E-13
---------------------------------------------------------------
Convergence criterion met in 10 iterations!
```

Including the solver scf section
in the input allows to specify the settings of the DFT calculation,
as e.g. the energy or residual thresholds, in more detail.
You may want to loosen the thresholds for the DFT 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
```