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Re^2: Raman tensor and raman activity calculation

Siarhei
kurhuzenkau@gmail.com


THANKS A LOT!
I've obtained correct results!

On Sat Aug 18 '12 6:59pm, Alex Granovsky wrote
----------------------------------------------
>Hi,

>I can confirm that Firefly uses the same equations to compute
>Raman intensities and activities as those used by you. My guess
>is that you do not use the same system of units as Firefly does.
>As depolarization ratios are dimensionless, you get the same
>values as computed by Firefly regardless of this.

>With Firefly, Raman activities has the dimension of Angstrom4/amu
>The computed polarizability derivatives components (in Bohr2) are
>first multiplied by the squared Bohr to Angstrom conversion factor
>(i.e., by 0.52917724924*0.52917724924). Then, they are projected onto
>mormal modes (i.e. dotted with normal modes) which are in amu-1/2 units.
>Finally, to compute a and g values, one need to square elements of
>Raman tensor so the final units are Angstrom4/amu

>Please check your units!

>Kind regards,
>Alex Granovsky
>
>
>
>
>
>On Sat Aug 18 '12 5:49pm, Siarhei wrote
>---------------------------------------
>>Hello!
>>I try to calculate Raman tensor from
>>Firefly output data (using ALPHA POLARIZABILITY
>>DERIVATIVE TENSOR and vibrational mode displacements),
>>when doing runtyp=RAMAN calculation .
>>Then, to check, whether the calculation of Raman tensor
>>was correct, or not, I calculate the Raman activity
>>and depolarization ratio directly from obtained Raman tensor.
>>(r=3g^2/(45a^2+4g^2), r is the depolarization ratio,
>>a-alpha, g-gamma - Raman tensor invariants;
>>R=45a^2+7g^2, R-raman activity)
>>So, the depolarization ratio obtained from
>>Raman tensor agree closely with depolarization
>>ratio, provided in Firefly output, but Raman activity don't.
>>Depolarization ratio agree closely with calculated,
>>what means, that gamma and alpha were calculated correctly.
>>I did these calculations for different vibrational
>>modes, and always depolarization ratio is correct, but
>>Raman activity is not.

>>Could you please tell how does Firefly calculate Raman activity?
>>Or, maybe, Firefly can print Raman tensor in
>>output file (there is some group or keyword)?

>>Thanks for any answer in advance.


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