Example: Constraint Linear Transit: H2O¶

#!/bin/sh

# 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 linearconstraints 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

eor

mv TAPE21 H2O.t21