Stishovite
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.
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.
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
External links
- https://en.wikipedia.org/wiki/Stishovite
- Structure of unit cell in 3D: [1]
