# Example: FDE freeze-and-thaw: HeCO2¶

`Download FDE_HeCO2_freezeandthaw.run`

```
#!/bin/sh
# This example demonstrates how a freeze-and-thaw FDE calculation can be
# performed. As test system, a He-CO2 van der Waals complex is used. It will
# further be shown how different exchange-correlation potential can be used for
# different subsystems, and how different basis set expansions can be employed.
# For details, see C.R. Jacob, T.A. Wesolowski, L. Visscher, J. Chem. Phys. 123
# (2005), 174104. It should be stressed that the basis set and integration grid
# used in this example are too small to obtain good results.
# Summary:
# - PW91 everywhere
# - SAOP for He; PW91 for CO2
# - FDE(s) calculation with PW91 everywhere
# Important, this kind of FDE geometry optimization only works with the non-
# default STO pair fitting method. This means that one has to include the key
# STOFIT in the input for ADF. If one does not use the BASIS key, like in this
# example, one should also include the key STOFIT in all fragment calculations
# (also in the create runs).
# Create atom
AMS_JOBNAME=C $AMSBIN/ams <<eor
System
Atoms
C 0.0 0.0 0.0
End
End
Task SinglePoint
Engine ADF
create C $AMSRESOURCES/ADF/TZ2P/C
stofit
Relativity Level=None
EndEngine
eor
mv C.results/adf.rkf t21.C
AMS_JOBNAME=O $AMSBIN/ams <<eor
System
Atoms
O 0.0 0.0 0.0
End
End
Task SinglePoint
Engine ADF
create O $AMSRESOURCES/ADF/TZ2P/O
stofit
Relativity Level=None
EndEngine
eor
mv O.results/adf.rkf t21.O
AMS_JOBNAME=He $AMSBIN/ams <<eor
System
Atoms
He 0.0 0.0 0.0
End
End
Task SinglePoint
Engine ADF
create He $AMSRESOURCES/ADF/TZ2P/He
stofit
Relativity Level=None
EndEngine
eor
mv He.results/adf.rkf t21.He
# == PW91 everywhere ==
# In the first part, the PW91 functional will be used for both the He and the
# CO2 subsystems. In this part, the FDE(m) basis set expansion is used, i.e.,
# basis functions of the frozen subsystem are not included in the calculation of
# the nonfrozen subsystem.
# First, the CO2 molecule is prepared. In this calculation, the C2v symmetry of
# the final complex is used, and the NOSYMFIT option has to be included because
# this molecule will be rotated as a frozen fragment.
############################
# Preparation of frozen CO2
############################
AMS_JOBNAME=CO2 $AMSBIN/ams <<eor
System
atoms [Bohr]
C 0.000000 0.000000 0.000000
O -2.192000 0.000000 0.000000
O 2.192000 0.000000 0.000000
end
end
Task SinglePoint
Engine ADF
eprint
scf NOPOP
sfo NOEIG NOOVL NOORBPOP
end
fragments
C t21.C
O t21.O
end
noprint BAS FUNCTIONS
nosymfit
numericalquality Good
stofit
symmetry C(2V)
title TEST 1 -- Preparation of frozen CO2
xc
gga pw91
end
Relativity Level=None
EndEngine
eor
mv CO2.results/adf.rkf t21.co2.0
# Afterwards, the FDE calculation is performed. In this calculation, the He atom
# is the nonfrozen system, and the previously prepared CO2 molecule is used as
# frozen fragment. For this frozen fragment the RELAX option is specified, so
# that the density of this fragment is updated in freeze-and-thaw iteration (a
# maximum number of three iteration is specified).
########################
# Embedding calculation
########################
AMS_JOBNAME=FDE $AMSBIN/ams <<eor
System
atoms [Bohr]
He 0.000000 0.000000 6.019000 adf.f=He
C 0.000000 0.000000 0.000000 adf.f=co2
O -2.192000 0.000000 0.000000 adf.f=co2
O 2.192000 0.000000 0.000000 adf.f=co2
end
end
Task SinglePoint
Engine ADF
eprint
scf NOPOP
sfo NOEIG NOOVL NOORBPOP
end
fde
fullgrid
pw91k
relaxcycles 3
end
fragments
He t21.He
co2 t21.co2.0 type=fde &
fdeoptions RELAX
SubEnd
end
noprint BAS FUNCTIONS
nosymfit
numericalquality Good
stofit
title TEST 1 -- Embedding calculation: He with frozen CO2 density -- freeze-and-thaw
xc
gga pw91
end
Relativity Level=None
EndEngine
eor
# == SAOP for He; PW91 for CO2 ==
# In this second part, the above example is modified such that PW91 is employed
# for the CO2 subsystem, while the SAOP potential is used for He. This can be
# achieved by choosing SAOP in the XC key (this sets the functional that will be
# used for the nonfrozen subsystem). Additionally, for the frozen fragment the
# XC option is used to chose the PW91 functional for relaxing this fragment.
# Furthermore, the PW91 functional is chosen for the nonadditive exchange-
# correlation functional that is used in the embedding potential with the
# GGAPOTXFD and GGAPOTCFD options in the FDE key.
########################
# Embedding calculation
########################
AMS_JOBNAME=FDE1 $AMSBIN/ams <<eor
System
atoms [Bohr]
He 0.000000 0.000000 6.019000 adf.f=He
C 0.000000 0.000000 0.000000 adf.f=co2
O -2.192000 0.000000 0.000000 adf.f=co2
O 2.192000 0.000000 0.000000 adf.f=co2
end
end
Task SinglePoint
Engine ADF
eprint
scf NOPOP
sfo NOEIG NOOVL NOORBPOP
end
fde
fullgrid
pw91k
relaxcycles 3
xcnadd PW91
end
fragments
He t21.He
co2 t21.co2.0 type=fde &
fdeoptions RELAX
XC GGA PW91
SubEnd
end
noprint BAS FUNCTIONS
nosymfit
numericalquality Good
stofit
title TEST 2 -- Embedding calculation: He with frozen CO2 density -- freeze-and-thaw
xc
model SAOP
end
Relativity Level=None
EndEngine
eor
rm t21.co2.0
# == FDE(s) calculation with PW91 everywhere ==
# In this third part, the PW91 functional is applied for both subsystems again,
# but in contrast to part 1, now the FDE(s) basis set expansion is used, i.e.,
# the basis functions of the frozen subsystem are included in the calculation of
# the nonfrozen subsystem. This can be achieved by employing the USEBASIS
# option. This option can be combined with the RELAX option.
############################
# Preparation of frozen CO2
############################
AMS_JOBNAME=CO2_PW91 $AMSBIN/ams <<eor
System
atoms [Bohr]
C 0.000000 0.000000 0.000000
O -2.192000 0.000000 0.000000
O 2.192000 0.000000 0.000000
end
end
Task SinglePoint
Engine ADF
eprint
scf NOPOP
sfo NOEIG NOOVL NOORBPOP
end
fragments
C t21.C
O t21.O
end
noprint BAS FUNCTIONS
nosymfit
numericalquality Good
stofit
symmetry C(2V)
title TEST 3 -- Preparation of frozen CO2
xc
gga pw91
end
Relativity Level=None
EndEngine
eor
mv CO2_PW91.results/adf.rkf t21.co2.0
########################
# Embedding calculation
########################
AMS_JOBNAME=FDE_PW91 $AMSBIN/ams <<eor
System
atoms [Bohr]
He 0.000000 0.000000 6.019000 adf.f=He
C 0.000000 0.000000 0.000000 adf.f=co2
O -2.192000 0.000000 0.000000 adf.f=co2
O 2.192000 0.000000 0.000000 adf.f=co2
end
end
Task SinglePoint
Engine ADF
eprint
scf NOPOP
sfo NOEIG NOOVL NOORBPOP
end
fde
fullgrid
pw91k
relaxcycles 3
end
fragments
He t21.He
co2 t21.co2.0 type=fde &
fdeoptions RELAX USEBASIS
SubEnd
end
noprint BAS FUNCTIONS
nosymfit
numericalquality Good
stofit
title TEST 3 -- Embedding calculation: He with frozen CO2 density -- freeze-and-thaw
xc
gga pw91
end
Relativity Level=None
EndEngine
eor
```