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AlKindi
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Like quinacridones or HgS and HgS [itex]\gamma[/itex]. I don't understand how crystal phase can act on the resonace of the electrons...Please reference! Thank!
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ZapperZ said:Different crystal geometry has different phonon modes and spectrum. The "colors" of such crystal is a direct function of the phonon characteristics.
Zz.
DrDu said:I don´t think that phonon modes are of importance in case of the examples you gave. I suspect that some electronic transitions are dipole forbidden in one crystal structure but not in the other. E.g. the molecules may form dimers in the crystal. In one crystal, the dimers are lying parallel to each other, in the other structure anti-parallel. Due to the coupling of the two molecules the electronic transitions split into one of higher frequency and one of lower frequency. Which of the two is of higher intensity depends on the relative orientation of the two molecules.
abhi2005singh said:Colors shown by the crystal depend upon various things and are related to the electronic structure and not on the phonon modes. Defects are one of these sources. Change in crystal structure can change the electronic structure of the material and hence the color of the crystal since it is related to the electronic transitions. If transition metal ions are present, change in crystal structure can change the splitting of the degenerate levels resulting in levels of various symmetries. The allowed electronic transitions depend on the symmetry of the ground state, the transition operator and the final state. Hence some the transition can be allowed while the others can be forbidden on change in the crystal symmetry. This can lead to change in color by changing the crystal structure.
Whatever I have mentioned above can be calculated, but I am not the correct person to say anything on as to how it is done.
Crystal phases have different colors because of their unique molecular structures and compositions. The arrangement of atoms in a crystal affects how it interacts with light, absorbing and reflecting different wavelengths, and thus producing different colors.
The range of colors in a crystal phase is dependent on the types of atoms present and their arrangements. Some crystal phases have a broader range of colors because they contain a greater variety of atoms and molecular structures, allowing for more diverse interactions with light.
Changes in a crystal phase's color can be caused by a variety of factors, such as changes in temperature, pressure, or chemical composition. These changes can alter the arrangement of atoms in the crystal, resulting in different interactions with light and a change in color.
Yes, there are crystal phases that are colorless. This is usually due to their molecular structure, which does not allow for significant interactions with light. However, some colorless crystals can appear to have a hue when viewed in large quantities due to light scattering.
While the color of a crystal phase can provide some information about its composition, it is not a reliable method of identification. Many crystal phases can have similar colors, and other properties such as density, hardness, and shape must be considered to accurately identify a crystal phase.