Example: FDE energy: NH3-H2O

Download FDE_Energy_NH3-H2O.run

This is example for a calculation of FDE interaction energies in ADF in case of closed shell fragments.

It performs single point runs for H2 O and NH3 with LDA/DZ (all-electron) and uses these fragments in:

  • an FDE energy embedding calculation calculation in which the energy of water in presence of a frozen ammonia is computed This requires a supermolecular integration grid
  • a fully variational FDE energy calculation (with freeze-and-thaw)

Integration accuracy is 6.0 which should give total energies for the fragments accurate at least up to 10**(-4) atomic units.

$ADFBIN/adf << EOF
Title H2O LDA/DZ single point
 ATOMS
         O        1.45838        0.10183        0.00276
         H        0.48989       -0.04206        0.00012
         H        1.84938       -0.78409       -0.00279
 END
 SYMMETRY tol=1e-2
 BASIS
   Type DZ
   Core None
 END
 XC
   LDA
 END
 INTEGRATION
  accint  6.0
 END
 NOSYMFIT
EOF
rm logfile
mv TAPE21 t21.water
EOF

In a similar way the N3 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. First an FDE energy embedding calculation calculation in which the energy of water in presence of a frozen ammonia is computed. This requires a supermolecular integration grid.

$ADFBIN/adf << EOF
Title NH3-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
         N       -1.51248       -0.03714       -0.00081    f=frag2
         H       -1.71021        0.95994       -0.11003    f=frag2
         H       -1.96356       -0.53831       -0.76844    f=frag2
         H       -1.92899       -0.35123        0.87792    f=frag2
 END
 SYMMETRY tol=1e-2
 FRAGMENTS
  frag1  t21.water
  frag2  t21.ammonia type=FDE
 END
 XC
   LDA
 END
 INTEGRATION
  accint  6.0
 END
 EXACTDENSITY
 FDE
   THOMASFERMI
   FULLGRID
   ENERGY
 END
EOF

Next a fully variational FDE energy calculation (with freeze-and-thaw) is performed.

$ADFBIN/adf << EOF
Title NH3-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
         N       -1.51248       -0.03714       -0.00081    f=frag2
         H       -1.71021        0.95994       -0.11003    f=frag2
         H       -1.96356       -0.53831       -0.76844    f=frag2
         H       -1.92899       -0.35123        0.87792    f=frag2
 END
 SYMMETRY tol=1e-2
 FRAGMENTS
  frag1  t21.water
  frag2  t21.ammonia type=FDE  &
     fdeoptions RELAX
  SubEnd
 END
 XC
   LDA
 END
 INTEGRATION
  accint  6.0
 END
 EXACTDENSITY
 SAVE TAPE21
 FDE
   THOMASFERMI
   RELAXCYCLES 3
   ENERGY
 END
EOF