imaginary frequency with MP2 freq calculation
Just Got Here
6:10:30 PM PDT - Wed, Jun 27th 2018
Hi guys,

I am new to NWChem and need your help regarding my calculation.

I have been having an imaginary frequency with mp2/cc-pvdz. I used tight convergence but didn't work. I ran the calculation with b3lyp/6-31G(d) and there is no any imaginary frequency. I then use the optimized b3lyp geometry and re-ran the calculation with mp2/cc-pvdz but still, an imaginary frequency was there. Please help out.

Find below the input file.

Thanks

Aliyu


echo

start AZE_BH3

title "Azetidine-borane mp2 calculation"
charge 0

geometry units angstroms print xyz
symmetry cs
  N        0.61545        0.38666        0.00000

  C        0.04980       -0.52334        1.06861

  C       -0.78839       -1.26043        0.00000

  C        0.04980       -0.52334       -1.06861

  H       -0.48198        0.04033        1.83150

  H        0.82804       -1.13780        1.52451

  H       -1.83491       -0.96091        0.00000

  H       -0.72026       -2.34733        0.00000

  H       -0.48198        0.04033       -1.83150

  H        0.82804       -1.13780       -1.52451

  H        1.63091        0.42476        0.00000

  B        0.04980        1.91323        0.00000

  H        0.48304        2.41812        1.01244

  H       -1.15828        1.81195        0.00000

  H        0.48304        2.41812       -1.01244
end

basis spherical
 * library cc-pVDZ
end

mp2
 # Exclude core electrons from MP2 treatment

 freeze atomic
end

task mp2 optimize
task mp2 freq

Forum Vet
11:55:41 AM PDT - Thu, Jun 28th 2018
Please use this modified input that makes use of tighter tolerances to get a more precise energy minimum and more accurate frequencies

start AZE_BH3

title "Azetidine-borane mp2 calculation"
charge 0

geometry units angstroms autosym 0.4 print xyz
#symmetry cs
   N        0.61545        0.38666        0.00000
   C        0.04980       -0.52334        1.06861
   C       -0.78839       -1.26043        0.00000
   C        0.04980       -0.52334       -1.06861
   H       -0.48198        0.04033        1.83150
   H        0.82804       -1.13780        1.52451
   H       -1.83491       -0.96091        0.00000
   H       -0.72026       -2.34733        0.00000
   H       -0.48198        0.04033       -1.83150
   H        0.82804       -1.13780       -1.52451
   H        1.63091        0.42476        0.00000
   B        0.04980        1.91323        0.00000
   H        0.48304        2.41812        1.01244
   H       -1.15828        1.81195        0.00000
   H        0.48304        2.41812       -1.01244
end

basis spherical
  * library cc-pVDZ
end

mp2
  # Exclude core electrons from MP2 treatment
  freeze atomic
  tight
end
driver
clear
tight
end

task mp2 optimize
task mp2 freq

Just Got Here
11:12:51 PM PDT - Sun, Jul 1st 2018
Thank you very much. It really worked. Cheers.


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