# Hartree-Fock calculation¶

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.

## Setting up an HF calculation¶

A Hartree-Fock (HF) calculation is performed by specifying a HF wavefunction in the method section of the input file. Available HF methods are RHF (hf), UHF (uhf), and MLHF (mlhf). E.g., for a RHF calculation we write

method
hf
end method


At the HF level, single-point calculation and geometry optimization can be performed. To select one of them, specify either ground state or ground state geoopt in the do section. E.g., for a single-point calculation

do
ground state
end do


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

system
name: H2O
charge: 0
end system

do
ground state
end do

method
hf
end method

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
end geometry


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 gradient thresholds, in more detail. You may want to loosen the thresholds for the HF calculation as the default energy and gradient thresholds ($$10^{-7}$$) are chosen to be rather tight. If you also want to get the molecular orbital coefficients, the print orbitals keyword has to be specified in this section.

solver scf
energy threshold:   1.0d-4
residual threshold: 1.0d-4
print orbitals
end solver scf


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.

Solver SCF

HF mean value