Difference between revisions of "Stishovite"

Revision as of 12:22, 1 March 2023

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.

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.

• Mechadensite

External links

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