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Re^4: Can we calculate Frequency dependent dielectric constant of any sample?

Siddheshwar Chopra

Dear Alex,
Thats not exactly the answer for what I asked. I want to know what should be the values of FREQ(1) for frequencies corresponding to 1MHz to 20GHz. As I understood from the FIREFLY manual, I can only  set a minimum of 0.000001 a.u. which corresponds to around 10e11 Hz. Thats the concern to me.. This range means that I can set a minimum of 100Ghz or so.. Please help.


n Sat Jun 22 '13 6:09am, Alex Granovsky wrote
>Dear Siddheshwar,

>you can specify up to 10 frequencies at once.
>Set nfreq to 10 and provide desired values
>in the freq array. It is recommended to set the
>first frequency to zero and enlist frequencies
>in ascending order. Note they are given in atomic
>units so you need to convert your MHz or GHz values
>to atomic units.

>Hope this helps.

>Kind regards,

>On Wed Jun 19 '13 2:24pm, Siddheshwar Chopra wrote
>>Dear Alex,
>>Thank you for the information. As per your input file, I ran the program to find polarizability of a molecule. I wish to ask that is it possible to give the FREQ(n) array for a range of 1MHz to 20GHz? Is it possible to get this frequency range in FIREFLY?


>>On Tue Jun 18 '13 8:02pm, Alex Granovsky wrote
>>>Dear Siddheshwar,

>>>dielectric constant is a macroscopic property.
>>>At microscopic level, we can compute frequency-dependent
>>>polarizabilities and hyper-polarizabilities. Having a certain
>>>model of the macroscopic body one can relate a microscopic
>>>properties such as polarizability to a dielectric constant.

>>>Below please find a sample file with computation of
>>>frequency-dependent polarizability for benzene molecule
>>>using PBE0 density functional. In brief, this is done
>>>using runtyp=TDHF and specifying some DFTTYP.
>>>If no DFTTYP is given, then these are indeed classical
>>>TDHF calculations, if DFTTYP is given then they in fact
>>>become TDDFT computations.


 $TDHF NFREQ=2 FREQ(1)=0,0.1 $END
Dnh       6

CARBON      6.0     -0.698164472         1.209256337         0.000000000
HYDROGEN    1.0     -1.241338149         2.150060743         0.000000000

>>>Kind regards,
>>>Alex Granovsky
>>>On Fri Jun 14 '13 11:00am, Siddheshwar Chopra wrote
>>>>Dear Sir,
>>>>I would be glad if you could throw some light on How to calculate the frequency dependent Dielectric constant using FIREFLY?? As far as I have read, DFPT is used to do the same... please help.


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