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Re^6: Calculation of dielectric constant at Freq= 1KHz.. Help needed.

Alex Granovsky


On Wed Jul 29 '15 2:44pm, Siddheshwar Chopra wrote
>Dear Alex,
>Please confirm if the procedure below is correct:

>The lines from end of file:

>  ISOTROPIC AVERAGE ALPHA =             165.20693058430660 A.U.


>Is this the electronic polarizability (in Hartrees)?

Yes this is electronic polarizability (in atomic units).

>If yes, then I just should use the Clausius–Mossotti relation to find epsilon (dielectric constant).

You cannot use the Clausius–Mossotti relation because
in the low frequency region you need to take into account
the nuclear contributions to polarizability as I explained

Kind regards,
Alex Granovsky

>Kind Regards,
>On Wed Jul 29 '15 2:31pm, Siddheshwar Chopra wrote
>>Dear Alex,
>>I completely agree with you on the static dielectric point. I got my answer. But could you also describe how this static dielectric constant is calculated from the TDHF calculation (attached earlier)? It would be a great help.

>>Kind regards,

>>On Wed Jul 29 '15 1:07am, Alex Granovsky wrote

>>>I believe at 1 KHz dielectric constant will be almost exactly as
>>>dielectric constant at 0 Hz i.e. the static one.
>>>Firefly calculates only electronic part of polarizability and hyper-
>>>polarizabilities. To compute dielectric constant at such a low
>>>frequency as 1 KHz you need also to know nuclear contributions
>>>to polarizability. It is impossible to compute them using Firefly.
>>>Note, polarizability is a property of micro-objects while dielectric
>>>constant is a macro-property. You need to use some model to deduce
>>>macro property from the micro one.

>>>Kind regards,
>>>Alex Granovsky
>>>On Fri Jul 24 '15 11:03am, Siddheshwar Chopra wrote
>>>>Dear Alex,
>>>>Please find attached the new output file.. Please tell me about the calculation of dielectric constant.

>>>>Kind Regards,

>>>>On Tue Jul 21 '15 4:56pm, Alex Granovsky wrote

>>>>>your input structure is invalid. The terminal C atoms should be properly terminated.

>>>>>Alex Granovsky
>>>>>On Tue Jul 14 '15 8:41am, Siddheshwar Chopra wrote
>>>>>>Dear Users,
>>>>>>This is the very first time that I have tried finding the dielectric constant using FIREFLY.. I have attached an output file for your reference. I wanted to find the dielectric constant at Frequency=1 KHz. For the same, I have added "1.519835E-13" to the Freq(1) array. I would be really grateful if you all can help me understand HOW to calculate the dielectric constant from the o/p file.
>>>>>>Also, as you can see, I have used classical calculations here.
>>>>>>In addition, I request Alex Sir to tell the Frequency range (in KHz) in which we can find the dielectric constant..
>>>>>>Kind Regards,

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