Example: Mobile Block Hessian: CH4¶

#! /bin/sh

# A frequency calculation is performed using the mobile block Hessian
# (MBH)method. The coordinates in the ATOMS section should be the partially
# optimized coordinates (or the fully optimized coordinates would work too).

# Such geometry optimization will not be discussed here any further. The next
# input for ADF shows how to perform a frequency calculation with MBH.


$AMSBIN/ams <<eor
System
  atoms
     C         0.000000    0.000000    0.000000
     H         0.634671    0.634671    0.634671
     H        -0.634671   -0.634671    0.634671
     H        -0.634671    0.634671   -0.634671
     H         0.634671   -0.634671   -0.634671
  end
end

Task SinglePoint
Properties
    NormalModes True
End

NormalModes
  Displacements Block
  BlockDisplacements
    BlockAtoms 1 2 3 4
    RadialDisplacement 0.001
  End
End

Engine ADF
  title Methane
  basis
    core None
    type DZ
    CreateOutput Yes
  end
  numericalquality verygood
  symmetry nosym
EndEngine
eor

# The quality of the frequencies/modes depends largely on the block choice. Best
# results are obtained when grouping atoms in a block if those atoms are known
# to form rather rigid structures. For instance, grouping the 11 atoms of
# benzene side group into a block, will usually result in representative
# frequencies. In this example the block choice is only illustrative for the
# methodology.