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

• Panthera Leo
In summary: The blue color of the Hope Diamond is due to the presence of boron which has a band gap of 0.4 eV. This means that the electron in boron can only absorb certain frequencies of light and as a result, it gives off a blue color.
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.

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Panthera Leo said:
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.

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Holy capslock Feynman.

Panthera Leo said:
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.

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cgk said:
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?

Drakkith said:
Holy capslock Feynman.

You reminded me of QED :)

Is it possible to use QED in this case?

Jacques_L said:
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?!

## 1. How do I determine the charge transfer complex in sapphire?

To determine the charge transfer complex in sapphire, you will need to perform spectroscopic measurements, such as UV-Vis or IR spectroscopy, and compare the results to known values for Fe2+ and Ti4+ charge transfer complexes. This will allow you to calculate the charge transfer ratio and determine the presence of the complex in sapphire.

## 2. What are the factors that affect the calculation of charge transfer complex in sapphire?

The factors that can affect the calculation of the charge transfer complex in sapphire include the purity of the sample, the concentration of Fe2+ and Ti4+, and the wavelength range used for the spectroscopic measurements. It is important to ensure that these factors are controlled and kept consistent for accurate results.

## 3. Can I use other techniques besides spectroscopy to calculate the charge transfer complex in sapphire?

While spectroscopy is the most commonly used technique for calculating the charge transfer complex in sapphire, other techniques such as X-ray crystallography and electron paramagnetic resonance (EPR) spectroscopy can also be used. These techniques can provide more detailed information about the complex and its structure.

## 4. How do I interpret the results of the charge transfer complex calculation?

The results of the charge transfer complex calculation will provide you with the ratio of Fe2+ and Ti4+ ions in the complex, which can indicate the degree of charge transfer between them. A higher ratio indicates a stronger charge transfer complex, while a lower ratio suggests a weaker complex. Additionally, the position and intensity of the absorption peaks in the spectroscopic measurements can provide further information about the complex.

## 5. What are some potential applications of studying the charge transfer complex in sapphire?

The study of the charge transfer complex in sapphire can have various applications, such as in the field of material science for understanding the electronic and optical properties of sapphire. It can also provide insights into the formation and stability of other charge transfer complexes, as well as their potential uses in areas such as catalysis and energy storage.

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