Example: FDE: H2O in water¶
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 also: C.R. Jacob, J. Neugebauer, L. Jensen and L. Visscher, Comparison of frozen-density embedding and discrete reaction field solvent models for molecular properties, Physical Chemistry Chemical Physics 8, 2349 (2006)
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.
$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 NumericalQuality good 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 NumericalQuality good 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