imaginary frequency with MP2 freq calculation

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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