In g09 Opt+Freq calculation i used the following comment in Route section
#P M062X/6-31G* Opt=(gdiis, CalcAll) scf=qc Freq TThe job was done fine but I found the frequency is calculated two times in the output. Can anybody please explain why it calculated two times
When you use the opt=CalcAll keyword, the frequency is automatically calculated, since it has already gone through the effort of calculating the Hessian for the final optimization step. Then you added the Freq keyword, so it calculated it a second time.
From G09 website:
CalcAll
Specifies that the force constants are to be computed at every point using the current method (available for the HF, MP2, CASSCF, DFT, CIS, and semi-empirical methods only). Note that vibrational frequency analysis is automatically done at the converged structure and the results of the calculation are archived as a frequency job.
When you use the opt=CalcAll keyword, the frequency is automatically calculated, since it has already gone through the effort of calculating the Hessian for the final optimization step. Then you added the Freq keyword, so it calculated it a second time.
From G09 website:
CalcAll
Specifies that the force constants are to be computed at every point using the current method (available for the HF, MP2, CASSCF, DFT, CIS, and semi-empirical methods only). Note that vibrational frequency analysis is automatically done at the converged structure and the results of the calculation are archived as a frequency job.
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