Example: FDE geometry optimization: NH3-H2O: FDE geometry optimization¶
This examples performs a structure optimization of H2 O in presence of frozen NH3 (via optimization of selected coordinates) with LDA and DZ basis. We need a high accint of 6.0 here because the potential energy surface is rather flat and small errors might lead to discrepancies in final structures. It uses (at present) the old branch optimizer for this purpose.
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).
First, the NH3 fragment is made. Next the FDE geometry optimization is performed with:
$ADFBIN/adf << eor TITLE NH3-H2O dimer FDE LDA DZ structure optimization of H2O STOFIT ATOMS N -1.01393958 -0.15260815 0.00000000 f=nh3 H -1.16290010 -1.15738765 0.00000000 f=nh3 H -1.49925696 0.21074929 0.81414267 f=nh3 H -1.49925696 0.21074929 -0.81414267 f=nh3 O Ox Oy Oz H H1x H1y H1z H H2x H2y H2z END GEOVAR Ox 2.25288687 Oy -0.00423586 Oz 0.00000000 H1x 1.28270504 H1y 0.05211069 H1z 0.00000000 H2x 2.54788803 H2y 0.90516678 H2z 0.00000000 END FRAGMENTS O t21.O_LDA_DZ H t21.H_LDA_DZ nh3 t21.NH3_LDA_DZ type=fde END FDE THOMASFERMI END XC LDA VWN END GEOMETRY Branch Old Optim Selected Iterations 100 ! (default is 30) END INTEGRATION 6.0 6.0 6.0 eor