HOW TO CALCULATE THE RESULTS OF Fe2+ Ti4+ CHARGE TRANSFER COMPLEX IN SAPPHIRE

[Panthera Leo]

hi,

I am trying to figure out how does the Ti4+ Fe2+ charge transfer complex produces the blue color of sapphire quantitavily... as it is given here:

http://www.webexhibits.org/causesofcolor/8.html"

How is it possible to calculate that this particular charge transfer requires absorption of "yellow light (~2eV)" giving rise to the complementary blue color, using very simple quantum physics because I am no expert ?

Is it possible to use bohr model and simple electromagnetism?

I will highly appreciate your contributions.

 

[cgk]

I am trying to figure out how does the Ti4+ Fe2+ charge transfer complex produces the blue color of sapphire quantitavily... as it is given here:

http://www.webexhibits.org/causesofcolor/8.html"

How is it possible to calculate that this particular charge transfer requires absorption of "yellow light (~2eV)" giving rise to the complementary blue color, using very simple quantum physics because I am no expert ?

That is not possible. Experts at computational chemistry for solids may be able to do this calculation, using lots of hardcore many-body physics and big computers, but even they would need to pull tricks[1]. And I still wouldn't bet on them being able to get quantitative agreement, let alone predictions. Using simple methods and not being an expert, I'm afraid you have no chance.

[1] The most commonly applied method for calculating excitation spectra, (linear-response) time dependent DFT, is not applicable to charge transfer excitations.

 

[Drakkith]

Holy capslock Feynman.

 

[Jacques_L]

hi,

I am trying to figure out how does the Ti4+ Fe2+ charge transfer complex produces the blue color of sapphire quantitavily... as it is given here:

http://www.webexhibits.org/causesofcolor/8.html"

How is it possible to calculate that this particular charge transfer requires absorption of "yellow light (~2eV)" giving rise to the complementary blue color, using very simple quantum physics because I am no expert ?

Is it possible to use Bohr model and simple electromagnetism?

Thank you for the reference to this paper. It is very clear and I long needed it.
The principle is easy to understand, the detailed calculations are beyond reach.
The principle is the same as in organic dyes : an electron can delocalize with oscillation between two distant and preferred zones of the molecule or the crystal. So the frequency of the oscillation is in the range of human-seeable band, and this electron can absorb several quanta at this frequency and thermalize them by mechanical means towards the lattice and its phonons, before reemitting a photon by optical way.

Colour is a property of the human system of sight (human retina, human wiring of the retina, human visual cortex), not of the light or the objects under light.

 

[Panthera Leo]

That is not possible. Experts at computational chemistry for solids may be able to do this calculation, using lots of hardcore many-body physics and big computers, but even they would need to pull tricks[1]. And I still wouldn't bet on them being able to get quantitative agreement, let alone predictions. Using simple methods and not being an expert, I'm afraid you have no chance.

[1] The most commonly applied method for calculating excitation spectra, (linear-response) time dependent DFT, is not applicable to charge transfer excitations.

I am trully stunned!

Actually I am a student of material science & I have been encountering such phenamena recently...

I am intrigued to know; what are the commonly applied methods for calculating excitation spectra?

 

[Panthera Leo]

Holy capslock Feynman.

You reminded me of QED :)

Is it possible to use QED in this case?

 

[Panthera Leo]

Thank you for the reference to this paper. It is very clear and I long needed it.
The principle is easy to understand, the detailed calculations are beyond reach.
The principle is the same as in organic dyes : an electron can delocalize with oscillation between two distant and preferred zones of the molecule or the crystal. So the frequency of the oscillation is in the range of human-seeable band, and this electron can absorb several quanta at this frequency and thermalize them by mechanical means towards the lattice and its phonons, before reemitting a photon by optical way.

Colour is a property of the human system of sight (human retina, human wiring of the retina, human visual cortex), not of the light or the objects under light.

Color is undoubtedly a magnificant phenamena to study from the scientific perspective... A combination of physics, chemistry, biology & so on ...

The hope diamond has a band gap of 0.4 eV due to Boron doped in its structure... How can the 0.4eV can give rise to blue diamond! just can't get this?!