Negative inelastic transmission

[rebeda]

Dear Sir,

According to my knowledge transmission, being a probability, can have minimum value of 0 and maximum of 1 (though it depends on the no. of channels available for conduction) and hence,  is always positive, but refering to one of your quantumwise tutorial-
link: http://quantumwise.com/support/tutorials/item/877-inelastic-electron-spectroscopy-of-h-molecule-between-1d-au-chains
I observe negative inelastic transmission at mode 0 and mode 5 in the IETS study of H molecule between 1D Au chains. I am not able to interpret this "negative inelastic transmission". In other words, how transmission can have negative values in this case, though for IETS, one can understand to have both positive and negative values.
Will you please help me?

Regards,
Rebeda

[Daniele Stradi]

You should interpret it as an enhancement or suppression of the elastic transmission, the total transmission (elastic+inelastic) will be always positive.

[rebeda]

Dear Sir,
 
Thank you so much for your reply.
In one of our systems we come across inelastic transmission ranging from -10 to +10 for both symmetric and asymmetric contributions due to certain phonon mode .This way the inelastic contributions comes 10 times of elastic contribution. Could you please help me to interpret it?

Awaiting for your kind reply.

Regards,
Rebeda

[Daniele Stradi]

It is impossible to say anything about this if you don't provide some details of the calculation such as a python script.

[rebeda]

Dear Sir,

In the IETS calculation were the vibrational normal modes evaluated in the harmonic approximation? If not, what type of approximation was used (ATK vnl 2015.1) ?

Awaiting your reply.

Regards,
Rebeda

[Petr Khomyakov]

Can you define normal modes not in the harmonic approximation?

[rebeda]

Dear Sir,

I got confused wether it is quasi-harmonic approximation or simply harmonic approximation?

Another small querry: how strongly the results of IETS(XLOE) in molecular junctions are supposed to depend on the exchange-correlation function ?
Thank a lot for your reply.

Regards,
Rebeda

[Petr Khomyakov]

I got confused whether it is quasi-harmonic approximation or simply harmonic approximation?

If your system volume is fixed, there is no point of using or talking about quasi-harmonic approximation.

Another small query: how strongly the results of IETS(XLOE) in molecular junctions are supposed to depend on the exchange-correlation function ?

It may depend on the choice of density functional, but that already holds true for the electron transport through molecular junctions without electron-phonon interaction included.  I guess this is where you have to first test your transport calculations.