Example: Constraint Linear Transit: H2O¶
The LINEARCONSTRAINTS keyword allows geometry optimizations (old branch) with constraints defined by arbitrary linear combinations of (internal) coordinates. The constraint has to be satisfied at the start of the geometry optimization.
Example for bond length constraint, where at the start of the linear transit rOH1=R1=1.0, and rOH2=R2=1.5, such that (-1.0)*R1+(1.0)*R2=0.5, and in the final geometry -R1+R2=0.0 (Reactcoord 0.5 0.0)
$ADFBIN/adf << eor
title constraint keyword
XC
GGA Becke Perdew
END
Geometry
Branch Old
LinearTransit 6
End
BeckeGrid
Quality good
End
Atoms Internal
O 0 0 0
H 1 0 0 R1
H 1 2 0 R2 109.9
End
GeoVar
R1 =1.
R2 =1.5
End
LinearConstraints
ReactCoord 0.5 0.0
R1 -1.0
R2 1.0
SubEnd
End
Basis
Type DZP
End
end input
eor