Difference between revisions of "Stishovite"
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Stishovite has a very high density for a SiO<sub>2</sub> polymorph ( 4.287 g/ccm ) this is because | Stishovite has a very high density for a SiO<sub>2</sub> polymorph ( 4.287 g/ccm ) this is because | ||
| − | in stishovite the silicon is octahedrally coordinated and bound to eight oxygen atoms instead of just four removing a lot of the voids in the crystal structure. | + | in stishovite the silicon is octahedrally coordinated and bound to eight oxygen atoms instead of just four removing a lot of the voids in the crystal structure. The oxygen atoms are threefold coordinated to titanium (rather than twofold coordinated like in most cases as e.g. in quartz). |
A polymorph of SiO<sub>2</sub> with a similar density is [[seifertite]] ( 4.294 g/cm3 ). | A polymorph of SiO<sub>2</sub> with a similar density is [[seifertite]] ( 4.294 g/cm3 ). | ||
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* [[Rutile structure]] | * [[Rutile structure]] | ||
* [[Rutile]] – same crystal structure and unit cell as stisovite <br>Systematically substituting some of stishovites silicon atoms for titanium atoms gives [[neo-polymorph]]s. <br> See: [[Mechadensite]] | * [[Rutile]] – same crystal structure and unit cell as stisovite <br>Systematically substituting some of stishovites silicon atoms for titanium atoms gives [[neo-polymorph]]s. <br> See: [[Mechadensite]] | ||
| + | * '''[[Base materials with high potential]]''' | ||
== External links == | == External links == | ||
Latest revision as of 14:20, 7 April 2025
Just like like common quartz stishovite is a polymorph of silicon dioxide (SiO2).
It may be of peculiar interest because of:
- its high hardness (mohs 8.5 to 9.5) compared to quartz (mohs 7 - defining mineral)
- it consisting of the two globally (and often locally) most common elements in earth crust
- it still featuring a reasonably simple (tetragonal) crystal structure with the rutile structure
Given both stishovite and rutile feature the same crystal structure it may be possible to mechanosynthesize checkerboard neo-polymorphic transitions by replacing some Si with with Ti in a regular pattern. Potentially improving eventual stability problems at low ambient pressures of only 1atm.
Stishovite is a metastable compound (like diamond and lonsdaleite but even harder to reach by non mechanosynthetic means) A substitution of Si with Ti (if possible in greater quantities) may (or may not) increase the stability against conversion back into more thermodynamically stable polymorphs such as quartz at higher temperatures.
Misc
Stishovite has a very high density for a SiO2 polymorph ( 4.287 g/ccm ) this is because in stishovite the silicon is octahedrally coordinated and bound to eight oxygen atoms instead of just four removing a lot of the voids in the crystal structure. The oxygen atoms are threefold coordinated to titanium (rather than twofold coordinated like in most cases as e.g. in quartz).
A polymorph of SiO2 with a similar density is seifertite ( 4.294 g/cm3 ). It is orthorhombic with a unit cell that perhaps is slightly more complex than stishovites simple rutile structure.
Related
- Seifertite
- Base materials with high potential
- Silicon
- Rutile structure
- Rutile – same crystal structure and unit cell as stisovite
Systematically substituting some of stishovites silicon atoms for titanium atoms gives neo-polymorphs.
See: Mechadensite - Base materials with high potential
External links
- https://en.wikipedia.org/wiki/Stishovite
- Structure of unit cell in 3D: [1]
