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