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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 Angstrom^{4}/amu

>The computed polarizability derivatives components (in Bohr^{2}) 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 Angstrom^{4}/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.

Sat Aug 18 '12 8:49pm

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