# Example: Mobile Block Hessian: CH4¶

Download MBH_CH4.run

#! /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

Properties
NormalModes True
End

NormalModes
Displacements Block
BlockDisplacements
BlockAtoms 1 2 3 4
End
End

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.