H₂O in water: frozen density embedding (FDE)

Sample directory: adf/FDE_H2O_128/

This example demonstrates how to use FDE in combination with a large environment, that is modeled as a superposition of the densities of isolated molecules. Here, the excitation energies of a water molecule surrounded by an environment of 127 water molecules. For details, see C.R. Jacob, J. Neugebauer, L. Jensen, L. Visscher, Phys. Chem. Chem. Phys., 2006 8: 2349.

This calculation consists of two steps:

• First a prototype water molecule is calculated.
• Next the embedding calculation of water in water is performed.

To reduce the amount of output the next lines are included in the adf calculations:

EPRINT
  SFO NOEIG NOOVL NOORBPOP
  SCF NOPOP
END
NOPRINT BAS FUNCTIONS

First, a prototype water molecule is calculated. The density of this isolated water molecules will afterwards be used to model the environment. Since this molecule will be used as a frozen fragment that is rotated and translated, the option NOSYMFIT has to be included.

$ADFBIN/adf << eor
Title Input generated by modco

UNITS
  length bohr
  angle degree
END

XC
LDA
END

SYMMETRY NOSYM

GEOMETRY
  sp
END

SCF
  iterations 50
  converge 1.0e-6 1.0e-6
  mixing 0.2
  lshift 0.0
  diis n=10 ok=0.5 cyc=5 cx=5.0 cxx=10.0
END
INTEGRATION 5.0 5.0

FRAGMENTS
  O  t21.DZP.O 
  H  t21.DZP.H 
END

ATOMS
 O       -11.38048700000000    -11.81055300000000     -4.51522600000000    
 H       -13.10476265095705    -11.83766918322447     -3.96954531282721    
 H       -10.51089289290947    -12.85330720999229     -3.32020577897331    
END

ENDINPUT
eor

mv TAPE21 t21.mol_1

Afterwards, the FDE calculation is performed. In this FDE calculation, there is one nonfrozen water molecule and the previously prepared water molecule is included as a frozen fragment that is duplicated 127 times. For this frozen fragment, the more efficient fitted density is used.

$ADFBIN/adf << eor
Title Input generated by modco

UNITS
  length bohr
  angle degree
END

XC
MODEL SAOP
END

SYMMETRY NOSYM

SCF
  iterations 50
  converge 1.0e-6 1.0e-6
  mixing 0.2
  lshift 0.0
  diis n=10 ok=0.5 cyc=5 cx=5.0 cxx=10.0
END

EXCITATION
  ONLYSING
  LOWEST  5
END

INTEGRATION 4.0 4.0

FRAGMENTS
  O      t21.DZP.O 
  H      t21.DZP.H 
  frag1  t21.mol_1 type=fde &
    fdedenstype SCFfitted
  SubEnd
END

ATOMS
 O         0.00000000000000      0.00000000000000      0.00000000000000    
 H        -1.43014300000000      0.00000000000000      1.10739300000000    
 H         1.43014300000000      0.00000000000000      1.10739300000000    
 O       -11.38048700000000    -11.81055300000000     -4.51522600000000    f=frag1/1  
 H       -13.10476265095705    -11.83766918322447     -3.96954531282721    f=frag1/1  
 H       -10.51089289290947    -12.85330720999229     -3.32020577897331    f=frag1/1  
 O        -1.11635000000000      9.11918600000000     -3.23094800000000    f=frag1/2  
 H        -2.82271357869859      9.71703285239153     -3.18063201242303    f=frag1/2  
 H        -0.12378551814273     10.53819303003839     -2.70860866559857    f=frag1/2  
...
 O         5.96480100000000      4.51370300000000      3.70332800000000    f=frag1/127 
 H         5.24291272273548      3.06620845434369      2.89384293177905    f=frag1/127 
 H         4.73614594944492      5.00201400735317      4.93765482424434    f=frag1/127 
END

FDE
  PW91K
END


ENDINPUT
eor