Neo-polymorph: Difference between revisions

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The patterns can be:
The patterns can be:
* different atom types (elements) ... specific example: A crossover gemstone between Rutile (polymorph of TiO<sub>2</sub>) and stishovite (polymorph of SiO<sub>2</sub>). The pattern making elements are Ti & Si. Oxygen atoms stay at their places.
* different stacking geometry or ... specific example: A crossover between Diamond (cubic stacking) and lonsdaleite (hexagonal stacking). (When pointing up a tetrapod of carbon bonds there are two ways one can orient the up facing three bonds in a six direction hexagon).
* different stacking geometry or ... specific example: A crossover between Diamond (cubic stacking) and lonsdaleite (hexagonal stacking). (When pointing up a tetrapod of carbon bonds there are two ways one can orient the up facing three bonds in a six direction hexagon).
* ...
* changes between different crystal structures of the same composition (adn stoichometry) so long nigh seamless covalent transitions are possible
Excluded here:
* different atom types (elements) fall under [[neo-isotypes]] instead: <br>specific example: A crossover gemstone between Rutile (polymorph of TiO<sub>2</sub>) and stishovite (polymorph of SiO<sub>2</sub>). The pattern making elements are Ti & Si. Oxygen atoms stay at their places.


Patterns:
Patterns:
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Of course arbitrary many elements/layertypes/... are allowed. A,B,C,D,...
Of course arbitrary many elements/layertypes/... are allowed. A,B,C,D,...


Note: '''Thermodynamic accessibility''' refers to all the crude processes available today (2020) that only allow to handle matter in statistical quantities: melting, mixing, cooling, pressurizing, irradiating, ... This explicitly excludes advanced [[mechanosynthesis]].
Note: '''Thermodynamic accessibility''' refers to all the crude processes available today (2020) that only allow to handle matter in statistical quantities: melting, mixing, cooling, pressurizing, irradiating, ([[cook mix and stir thermodynamic synthesis]]) ... This explicitly excludes advanced [[mechanosynthesis]].


{{wikitodo| ABABAB ABCABC - no same letters following adjacently in case of SiC structure - fix discussion above accordingly eventually}}
{{wikitodo| ABABAB ABCABC - no same letters following adjacently in case of SiC structure - fix discussion above accordingly eventually}}
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See: [[pseudo phase diagrams]] for more details on this.
See: [[pseudo phase diagrams]] for more details on this.


'''The rutile stishovite (TiO<sub>2</sub> to strong SiO<sub>2</sub>) neopolymorphic transition:''' <br>
The common mineral [[rutile]] and the rare mineral [[stishovite]] (made out of the two most common elements in earth crust) share the same crystal structure. The rutile structure.
Albeit rutile not drawing silicon into its structure naturally (meaning it's thermodynamically unfavourable)
(as can be seen with rutile occuring embedded in quartz https://commons.wikimedia.org/wiki/File:Rutile@quartz.jpg)
a forced substitution (at least to some degree) may very well be possible via [[mechanosynthesis|mechanosyntheic]] means
and the resulting product [[base material]] may very well be highly (meta) stable at room temperature.
'''The quartz to "carbexplosoquartz" (SiO<sub>2</sub> to solid CO<sub>2</sub>) neopolymorphic transition''' <br>
Obviously CO<sub>2</sub> very much likes to be a gas (small atomic radii => sp orbitals sticking far out => orbitals hybridize and form double bonds)
so if pure CO is even mechanosynthsizable it would be a very delicate and thus dangerous high explosive. A little bit of substitution of Si with C may be safely forcable via mechanosynthetic means though, despite that substitution is not naturally happening due to unvafourable thermodynamics. Maybe even as much as 50% of the silicon could be substituted with carbon without getting to something unstable and useless? Who knows.
'''The SiO<sub>2</sub> to GeO<sub>2</sub> and SnO<sub>2</sub> neopolymorphic transition''' <br>
Si has a bit more dissimilarity to the element above (C) than the elements below (Ge,Sn) with the exception of (Pb).
Like less relative difference in diameter, less difference in their dislike to form double bonds, less difference in their metallicity, ... .
So these elements may be substitutable in higher quantities. Though Ge and Sn are to rare to be of use as large volume structural base material.
Also Ge and Sn form rutile structure (argutite and cassiereite respectively), so they may instead be able to
tie into the aforementioned rutile stishovite neopolymorphic transition.
Lead (Pb) may very well already be way too different to Si to even be force substitutable making the resulting structures unstable at room temperature or even below.
Lead and tin are (and where) used in the floating glass production process because they don't like to mix too much (on their own volition).
Still a lot of unwettability and immiscibility may be possible to overcome via mechanosynthetic forcing.
Also there is lead glass ({{TODO| find out how lead integrates in glass in the case of lead glass}})
* '''The Si<sub>3</sub>N<sub>4</sub> to beta carbon nitride C<sub>3</sub>N<sub>4</sub> neopolymorphic transition''' <br>
Both are high performance materials but [[beta carbon nitride]] is highly exotic even in its pure form today (2020).
[[Beta carbon nitride]] may be of especial interest since when drawing solid building material form thin air alone
The concentration of CO<sub>2</sub> is the limiting factor and given more than halve of C<sub>3</sub>N<sub>4</sub> is nitrogen
and thus material may be drawable more than double the speed.
* '''The BN to AlN neopolymorphic transition''' <br>
Pure AlN hydrolyzes with water, so when going far with the forced substitutuion the parts must be perfectly sealed against humidity.
* '''The tistarite to leukosapphire to diboron trioxide (Ti<sub>2</sub>O<sub>3</sub> to Al<sub>2</sub>O<sub>3</sub> to B<sub>2</sub>O<sub>3</sub>) neopolymorphic transition''' <br>
Pure B<sub>2</sub>O<sub>3</sub> is slightly water soluble and toxic, so when going far with the forced substitutuion the parts must be perfectly sealed against humidity.


== Related ==
== Related ==

Revision as of 11:38, 26 September 2025

(wiki-TODO: There is a significant mixup with neo-isotypes here. Move relevant parts to the new page.)

This article defines a novel term (that is hopefully sensibly chosen). The term is introduced to make a concept more concrete and understand its interrelationship with other topics related to atomically precise manufacturing. For details go to the page: Neologism.


A neo-polymorphic compound (or neo-isomorphic compound) is a highly (meta)stable non equilibrium polymorph of a material with a certain fixed stoichiometry that is exclusively accessible through mechanosynthesis. If just one element is involved the term neo-allotrope can be applied instead.

This includes patterns where specifically ordered states are thermodynamically not more attractive than disordered (or in other undesired form ordered) states but where a (sufficiently) high activation energy lies between the ordered and unordered states.

The patterns can be:

  • different stacking geometry or ... specific example: A crossover between Diamond (cubic stacking) and lonsdaleite (hexagonal stacking). (When pointing up a tetrapod of carbon bonds there are two ways one can orient the up facing three bonds in a six direction hexagon).
  • changes between different crystal structures of the same composition (adn stoichometry) so long nigh seamless covalent transitions are possible

Excluded here:

  • different atom types (elements) fall under neo-isotypes instead:
    specific example: A crossover gemstone between Rutile (polymorph of TiO2) and stishovite (polymorph of SiO2). The pattern making elements are Ti & Si. Oxygen atoms stay at their places.

Patterns:

  • ABABBABBBBAABABAABAA – unwanted unordered state – may be the only one that is thermodynamically accessible
  • ABABABABABABABABABAB – unwanted ordered state – may be the only one that is thermodynamically accessible
  • ABBAABBAABBAABBAABB – neo-polymorph – wanted peculiarly ordered state – not thermodynamically accessible - but accessible via mechanosynthesis

Of course arbitrary many elements/layertypes/... are allowed. A,B,C,D,...

Note: Thermodynamic accessibility refers to all the crude processes available today (2020) that only allow to handle matter in statistical quantities: melting, mixing, cooling, pressurizing, irradiating, (cook mix and stir thermodynamic synthesis) ... This explicitly excludes advanced mechanosynthesis.

(wiki-TODO: ABABAB ABCABC - no same letters following adjacently in case of SiC structure - fix discussion above accordingly eventually)

Examples

See: pseudo phase diagrams for more details on this.


Related

Examples:

Examples with likely missing end members

Take gem grade silicon carbide aka moissanite as starting point.
Then increasinvgly substitute the silicon Si atoms with titanium Ti atoms in a checkerboard fashion.
It is known that pure TiC likes to be in simple cubic rock salt structure, so at some degree of substitution.
the structure might become weakly metastable (worst case explosive) or entirely unstable.

Revesely, staring with simple cubic rock salt structure TiC and
substituting Ti with Si (or Ge) in checkerboard fashion seem more limited if possible at all.

Titanium carbide MXenes Ti2C1, Ti3C2, Ti4C3(?)
Might be checkerboard pattern Si/Ge substitutable by some degree.
Due to todays experimental syntehsis route via MAX phases and etching out A,
it is likely unclear in how far titanium carbide MXenescan be extended from
2D materials to a 3D materials that in the limit have Ti1C1 stoichometry.
That is: In how far they are metastable to transformation to
the known to be low energy stable simple cubic rock salt structure polymorph of TiC.

Side-note: MXenes have dense fcc==ccp structure akin to many metals.
Unlike moissanite and dioamondoids in general which are sparse,
half the atomic coordination, and voids due to being two interspersed fcc lattices.

External links

Wikipedia pages:

  • Isotype: (de) Translated citation: "Minerals of the same structural type are called isotypes. They crystallize in the same class of crystals and form similar crystal forms. "
  • Isotype: (wikipedia de) Isotyp
  • www.mineralienatlas.de
    lists minerals with equal or similar structures for any given mineral
    so thhis can serve as a possible starting point to find potential neo-polymorphs
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