# Example: FDE geometry optimization: H2O-Li(+)¶

Download GO_FDE_H2O-Li.run

This examples checks the gradient implementation for FDE. It performs a structure optimization H2O-Li(+) with LDA/DZP.

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 fragments are made, Li+ , and water. Next the FDE geometry optimization is performed with:

\$ADFBIN/adf << eor
TITLE H2O-Li(+) FDE/LDA/DZP GO New Optimizer starting at too short Li-O distance
STOFIT
ATOMS
Li      0.000000000000       0.000000000000      -0.054032208082
O       0.000000000000       0.000000000000      -1.534032208080  f=water
H      -0.778216093965       0.000000000000      -2.135966332900  f=water
H       0.778216093965       0.000000000000      -2.135966332900  f=water
END
CHARGE 1.0
FRAGMENTS
Li    t21.Li.LDA.DZP
water t21.water.LDA.DZP type=fde
END
XC
LDA VWN
END
FDE
ThomasFermi
END
GEOMETRY
Optim Delocalized
iterations 15