Example: Mobile Block Hessian (MBH): Ethanol

Download MBH_Ethanol.run

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). The next input for ADF shows how to perform a frequency calculation with MBH. The flag b=b1 in the ATOMS section adds the label ‘b1’ to some of the atoms. Only the four atoms labeled ‘b1’ (CH₃ ) will be considered as a block with fixed internal geometry.

$ADFBIN/adf <<eor
TITLE ethanol: second derivatives with MBH approach. CH3 is treated as a rigid block

ATOMS
1 C      -0.029587   -0.006554    0.008124     b=b1
2 H      -0.087498   -0.025163    1.109913     b=b1
3 H       1.027473   -0.056237   -0.302751     b=b1
4 H      -0.565305   -0.891154   -0.376242     b=b1
5 C      -0.694908    1.238909   -0.501807     b=b2
6 H      -0.670258    1.265092   -1.608847     b=b2
7 O      -2.069894    1.175059   -0.017251
8 H      -0.182335    2.138977   -0.109315     b=b2
9 H      -2.586972    1.972802   -0.317216
END

SYMMETRY nosym

BASIS
  type DZ
  core Large
  CreateOutput None
END

XC
LDA SCF VWN
END

GEOMETRY
   frequencies
   mbh b1
   branch new
END

NumericalQuality good
End input
eor

For comparison in this example also a calculation is performed without any restrictions.

$ADFBIN/adf <<eor
TITLE ethanol: complete vibrational spectrum, compare with MBH above

ATOMS
1 C      -0.029587   -0.006554    0.008124
2 H      -0.087498   -0.025163    1.109913
3 H       1.027473   -0.056237   -0.302751
4 H      -0.565305   -0.891154   -0.376242
5 C      -0.694908    1.238909   -0.501807
6 H      -0.670258    1.265092   -1.608847
7 O      -2.069894    1.175059   -0.017251
8 H      -0.182335    2.138977   -0.109315
9 H      -2.586972    1.972802   -0.317216
END

BASIS
  type DZ
  core Large
  CreateOutput None
END

XC
LDA SCF VWN
END

AnalyticalFreq
End

NumericalQuality good
End input
eor