# Example: FDE energy: unrestricted fragments: Ne-H2O¶

Download FDE_Energy_H2O-Ne_unrestricted.run

This is example for a calculation of FDE interaction energies in ADF for an open-shell frozen fragment.

It performs single point runs for H2O and Ne, the latter unrestricted with LDA/DZ (all-electron) and uses these fragments in an FDE energy embedding calculation in which the energy of water in presence of a frozen (open-shell) neon atom is computed. This is a bit of an artificial example but it serves its purpose.

No freeze-thaw is done, this is at present not possible with unrestricted (open shell) fragments, but has to be done manually.

Integration quality is good which should give total energies for the fragments accurate at least up to 10**(-4) atomic units.

This test has been checked to yield the same energy as a run with a closed- shell (restricted) Ne atom (just comment UNRESTRICTED in the input below). First the Ne and H2 O fragments are calculated.

$ADFBIN/adf << EOF Title Ne LDA/DZ single point, unrestricted ATOMS Ne -1.51248 -0.03714 -0.00081 END UNRESTRICTED BASIS Type DZ Core None END ZlmFit Quality good END BeckeGrid Quality good END SCF iterations 100 converge 1.0e-06 1.0e-06 END EXACTDENSITY NOSYMFIT EOF rm logfile mv TAPE21 t21.ne EOF  In a similar way the H2 O fragment is calculated. Next the FDE calculation is performed. The subkey ENERGY of the key FDE is used, such that the total FDE energy and FDE interaction energy is calculated. $ADFBIN/adf << EOF
Title Ne-H2O LDA/Thomas-Fermi/DZ FDE single point with interaction energy

ATOMS
O        1.45838        0.10183        0.00276    f=frag1
H        0.48989       -0.04206        0.00012    f=frag1
H        1.84938       -0.78409       -0.00279    f=frag1
Ne      -1.51248       -0.03714       -0.00081    f=frag2
END

SYMMETRY tol=1e-2

FRAGMENTS
frag1  t21.water
frag2  t21.ne type=FDE
END

ZlmFit
Quality good
END

BeckeGrid
Quality good
END

SCF
iterations  100
converge 1.0e-06 1.0e-06
END

EXACTDENSITY

FDE
THOMASFERMI
FULLGRID
ENERGY
END
EOF