Thomas Pijper
thomaspijper@hotmail.com
>there is a typo in the formula given by Thomas. It should read
>f_mn = 2/3 * (E_n - E_m) * (d_mn^2)
That's indeed what the formula should read, thanks for correcting.
Kind regards,
Thom
On Mon Jun 16 '14 10:08pm, Alex Granovsky wrote
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>Dear Michal,
>Dear Thomas,
>there is a typo in the formula given by Thomas. It should read
>f_mn = 2/3 * (E_n - E_m) * (d_mn^2)
>where d_mn is the norm of the transition dipole. I.e. the norm of
>transition dipole should be squared in the correct expression.
>As to transition velocity, for the exact solution of the molecular
>Schrodinger equation (SE), oscillator strength can be also expressed as:
>f_mn = 2/3 * (v_mn^2)/(E_n - E_m)
>where v_mn^2 is the squared norm of the transition velocity.
>This gives the alternative way of computing f_mn. For finite (incomplete)
>basis sets and approximate methods of solving SE the two expressions
>above are no longer equal. The first of them is considered to me the
>most accurate as transition velocity is more sensitive to the quality
>of wavefunction.
>Hope this helps.
>Kind regards,
>Alex Granovsky
>
>
>
>
>
>On Thu Jun 12 '14 10:49pm, Thomas Pijper wrote
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>>Dear Michal,
>>1) Currently, selection of CSFs or determinants at the MCSCF stage is not possible.
>>2) For the probability of an excitation, one should typically use the transition dipole moment. It can be converted to an oscillator strength by the formula:
>>f_mn = 2/3 * (E_n - E_m) * d_mn (assuming all values are in atomic units)
>>Hereby, you can use PT2 energies from the (X)MCQDPT2 calculation for E_m and E_n. Note that the printed dipole moment (d_mn) is determined at the zeroth-order level, not the PT2 level.
>>Oscillator strengths are IMO more useful when considering the probability of excitations as an oscillator strength correlates directly to the area of an absorption band in a UV/vis absorption spectrum.
>>
>>
>>Kind regards,
>>Thom
>>
>>
>>
>>
>>On Wed Jun 11 '14 4:52pm, Michal P Krompiec wrote
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>>>Hello, I have 2 questions:
>>>1) $XMCQDPT ISELCT=4 $END "allows selection of important CSFs". Does it work only at the PT2 stage, or also in MC-SCF? Is it possible to discard "unimportant" CSFs at MC-SCF stage?
>>>2) Regarding the output of XMCQDPT runs. Which value is more related to probability of radiative transition - transition dipole norm or dipole velocity norm? What is the practical difference between these and oscillator strengths?
>>>Thanks,
>>>Michal