Example: Constraint Geometry Optimization: H2O

Download GO_constraints.run

The key CONSTRAINTS can only be used in case of the New branch for optimization of coordinates. The input for this key is very similar to that of the RESTRAINT keyword. The key CONSTRAINTS can, however, also be used to constrain Cartesian coordinates. Note that the key RESTRAINT and freezing of coordinates with the GEOVAR key can also be used in the New branch for optimization of coordinates.

The constraints do not have to be satisfied at the start of the geometry optimization.

Example for angle restraint

$ADFBIN/adf << eor
title WATER geometry optimization with angle constraint
ATOMS
    1.O         0.001356    0.000999    0.000000
    2.H         0.994442   -0.037855    0.000000
    3.H        -0.298554    0.948531    0.000000
END
BASIS
 Type DZP
END
CONSTRAINTS
  ANGLE  3 1 2 125.0
END
GEOMETRY
  OPTIM DELOCAL
END
endinput
eor

Example for fixed-atom constraint. Note that the optimization should be done in Cartesian.

$ADFBIN/adf << eor
title WATER geometry optimization with fixed-atom constraint
ATOMS
    1.O         0.001356    0.000999    0.000000
    2.H         0.994442   -0.037855    0.000000
    3.H        -0.298554    0.948531    0.000000
END
BASIS
 Type DZP
END
SYMMETRY NOSYM
CONSTRAINTS
  ATOM 1 0.0 0.0 0.0
  ATOM 2 1.0 0.0 0.0
END
GEOMETRY
  OPTIM CARTESIAN
  BRANCH NEW
END
endinput
eor

Example for bond length restraint.

$ADFBIN/adf << eor
title WATER Geometry Optimization with bond length constraint
ATOMS
    1.O         0.001356    0.000999    0.000000
    2.H         0.994442   -0.037855    0.000000
    3.H        -0.298554    0.948531    0.000000
END
BASIS
 Type DZP
END
CONSTRAINTS
  DIST  1 2 1.03
  DIST  1 3 1.03
END
GEOMETRY
  OPTIM CARTESIAN
  BRANCH NEW
END
endinput
eor

Example for dihedral angle restraint

$ADFBIN/adf << eor
Title Constraining dihedral of ethane
SYMMETRY NOSYM
ATOMS
  1.C        -0.004115   -0.000021    0.000023
  2.C         1.535711    0.000022    0.000008
  3.H        -0.399693    1.027812   -0.000082
  4.H        -0.399745   -0.513934    0.890139
  5.H        -0.399612   -0.513952   -0.890156
  6.H         1.931188    0.514066    0.890140
  7.H         1.931432    0.513819   -0.890121
  8.H         1.931281   -1.027824    0.000244
END
CONSTRAINTS
  DIHED   6    2    1    3     20.00
END
BASIS
  type DZP
END
GEOMETRY
  OPTIM DELOCAL
END
endinput
eor

Example for Block constraint (with a dihedral constraint).

$ADFBIN/adf << eor
Title Block constraints (with a dihedral constraint)
SYMMETRY NOSYM
ATOMS
  1.C        -0.004115   -0.000021    0.000023 b=b1
  2.C         1.535711    0.000022    0.000008 b=b2
  3.H        -0.399693    1.027812   -0.000082 b=b1
  4.H        -0.399745   -0.513934    0.890139 b=b1
  5.H        -0.399612   -0.513952   -0.890156 b=b1
  6.H         1.931188    0.514066    0.890140 b=b2
  7.H         1.931432    0.513819   -0.890121 b=b2
  8.H         1.931281   -1.027824    0.000244 b=b2
END
CONSTRAINTS
  DIHED   6    2    1    3     20.00
  BLOCK b1
  BLOCK b2
END
BASIS
  type DZP
END
GEOMETRY
  OPTIM DELOCAL
END
endinput
eor