View source for Binary gem-like compound

'''Binary diamondoid compounds''' are [[diamondoid compounds]] that are constituted out of just two chemical elements. 

= Possible motivations for preferring them over single element compounds (allotropes) = 

* desired biodegradability
* making use of abundant reactive elements like e.g. calcium beside just carbon silicon and maybe boron  
* better accessibility of these materials in earlier productive nanosystems
* access of properties that are not emulatable by bond topology and bond strain alone (that is by metamaterial structure) most prominently electronic properties

= An exhaustive list of the binary compounds of interest is possible =

There aren't that many elements in the periodic table that are available in vast abundance.
Systematically combining them to pairs does leas to a manageable amount of possibilities. A pretty exhaustive list can be given.
After checking for the stability and suitability of these compounds the list of the ones that turn out to seem suitable as structural building materials
become even shorter.

Many [[Ternary and higher diamondoid compounds|ternary compounds]] can be derived from binary ones by suitable substitution of atoms. For orientation something like [[pseudo phase diagrams]] can be used.

= Classification by resistance against water =

== binary compounds that do not react or dissolve in water ==

One important subclass of the water stable binary compounds are the [[passivation layer mineral|'''passivation layer minerals''' of today's industrial metals]]. <br>
A big advantage of them is that their effect on human skin (in bulk contact - not nanoparticle form!) is widely known to be safe for most of them. <br>
Other binary water stable compounds are:

* SiC [http://en.wikipedia.org/wiki/Silicon_carbide '''silicon carbide'''] [http://en.wikipedia.org/wiki/Moissanite mossanite] - transparent when pure
* B<sub>4</sub>C [http://en.wikipedia.org/wiki/Boron_carbide boron carbide]
* SiB<sub>4</sub>; SiB<sub>6</sub> ? [http://en.wikipedia.org/wiki/Silicon_boride silicon boride]
* AlB<sub>12</sub> [http://en.wikipedia.org/wiki/Aluminium_dodecaboride aluminium dodecaboride] - hard
* β-C<sub>3</sub>N<sub>4</sub> [//en.wikipedia.org/wiki/Beta_carbon_nitride beta carbon nitride] (possibly a health hazard if cyanide release can occur - '''to investigate''')
* Si<sub>3</sub>N<sub>4</sub> [http://en.wikipedia.org/wiki/Silicon_nitride silicon nitride]
* cubic BN [http://en.wikipedia.org/wiki/Boron_nitride#Cubic_boron_nitride cubic boron nitride] - very similar to diamond (also cubic and hexagonal "allotropes")
* BP [http://en.wikipedia.org/wiki/Boron_phosphide boron phosphide] - transparent and chemically very stable
* CaB<sub>6</sub> [http://en.wikipedia.org/wiki/Calcium_hexaboride calcium hexaboride] - non water soluble earth alkali compound which is uncommon - irritating
* SiO<sub>2</sub> [http://en.wikipedia.org/wiki/Quartz quartz] (it's actually slightly water soluble) & allotropes like [http://en.wikipedia.org/wiki/Stishovite dense and hard stishovite] '''(Mohs 9-9.5 !!)'''
* Tectosilicates: [http://www.foresight.org/Conferences/MNT05/Papers/Gillett1/] [http://www.foresight.org/Conferences/MNT05/Papers/Gillett2/]
* Al<sub>2</sub>O<sub>3</sub> [http://en.wikipedia.org/wiki/Aluminium_oxide aluminum oxide] aka [http://en.wikipedia.org/wiki/Corundum corundum] or [http://en.wikipedia.org/wiki/Sapphire sapphire]
* Fe<sub>3</sub>C [http://en.wikipedia.org/wiki/Cementite iron carbide aka cementite]
* iron silicides & iron borides ? - unknown properties
* FeS<sub>2</sub> FeS iron sulfides - [http://en.wikipedia.org/wiki/Pyrite pyrite] and [http://en.wikipedia.org/wiki/Marcasite marcasite] ...
* Fe<sub>2</sub>O<sub>3</sub> [http://en.wikipedia.org/wiki/Hematite hämatite]
* Fe<sub>3</sub>O<sub>4</sub> [http://en.wikipedia.org/wiki/Magnetite magnetite]
* FeO [http://en.wikipedia.org/wiki/W%C3%BCstite wüstite]
* Cu<sub>3</sub>P [http://en.wikipedia.org/wiki/Copper%28I%29_phosphide copper(I) phosphide] (copper is not too abundant)
* Cu<sub>X</sub>S<sub>Y</sub> [http://en.wikipedia.org/wiki/Copper_sulfide copper sulfides] CuS [http://en.wikipedia.org/wiki/Covellite covellite], Cu2S [http://en.wikipedia.org/wiki/Chalcocite chalcocite], many more ...
* B<sub>6</sub>O [http://en.wikipedia.org/wiki/Boron_suboxide boron suboxide] (hardest known oxide)

Theres is a big stable group of B-C-N compounds, a few aluminum (Al2O3,AlB) and few silicon (SiC,SiO2,N4Si3) compounds.

There seem to be no binary [http://en.wikipedia.org/wiki/Category:Iron_minerals iron minerals] that have hardness above mohs 6.5

'''[[Titanium]]''' forms chemically and mechanically rather stable compounds with many nonmetals.
* TiC [http://en.wikipedia.org/wiki/Titanium_carbide titanium carbide]
* TiSi<sub>2</sub> [http://en.wikipedia.org/wiki/Titanium_disilicide titanium disilicide] (unknown mechanical properties ?)
* TiB<sub>2</sub> [http://en.wikipedia.org/wiki/Titanium_diboride titanium diboride]
* TiN [http://de.wikipedia.org/wiki/Titannitrid titanium nitride]
* TiP [http://en.wikipedia.org/wiki/Titanium%28III%29_phosphide titanium(III) phoshide] (metallic conductivity)
* titanium sulphides [http://en.wikipedia.org/wiki/Titanium%28II%29_sulfide TiS] (goldbrown), [http://en.wikipedia.org/wiki/Titanium_disulfide TiS<sub>2</sub>] (bronze/golden yellow), Ti<sub>2</sub>S<sub>3</sub> (black,graphitic), TiS<sub>3</sub>, Ti<sub>3</sub>S<sub>4</sub>, Ti<sub>4</sub>S<sub>5</sub>, Ti<sub>4</sub>S<sub>8</sub>, Ti<sub>8</sub>S<sub>9</sub>
* TiO<sub>2</sub> Ti<sub>2</sub>O<sub>3</sub> titanium oxide polymorphs: [http://en.wikipedia.org/wiki/Rutile rutile] [http://en.wikipedia.org/wiki/Anatase anatase] [http://en.wikipedia.org/wiki/Brookite brookite]

==binary compounds which very slowly dissolve in water and are thought to be rather nontoxic==

Solubility is good for an envirounmental viewpoint (decay time of abandoned scrap material) but bad for engineering materials.
Especially in nanosystems the slightes bit of dissolvation completely destroys the outermost layer of nanomachinery.
This makes sealing of products and high system reduncancy even more necessary than it is when more stable materials are used.

* Al<sub>4</sub>C<sub>3</sub> [http://en.wikipedia.org/wiki/Aluminium_carbide aluminum carbide]  - hydrolyses to aluminum hydroxide and methane
* AlN [http://en.wikipedia.org/wiki/Aluminium_nitride aluminum nitride] - oxidizes in air @ room temperature (layer <= 10nm) - hydrolyzes slowly in water to aluminum oxide and ammonia
* S<sub>2</sub>N<sub>2</sub> [http://en.wikipedia.org/wiki/Disulfur_dinitride disulfur dinitride] shock sensitive - decomposes explosively above 30°
* S<sub>4</sub>N<sub>4</sub> [http://en.wikipedia.org/wiki/Tetrasulfur_tetranitride tetrasulfur tetranitride] explosive decomposition to nitrogen and sulfur 4N<sub>2</sub> + S<sub>8</sub>
* (SN)<sub>X</sub> [http://en.wikipedia.org/wiki/Polythiazyl polythiazyl] - conductive inorganic polyner chain
* P [http://en.wikipedia.org/wiki/Allotropes_of_phosphorus the allotropes of elementar phosphorus]
* S [http://en.wikipedia.org/wiki/Allotropes_of_sulfur the allotropes of elementar sulfur]

simplest most water stable compounds of abundant alkaline eart metals
* MgO [http://en.wikipedia.org/wiki/Periclase periclase] also [http://en.wikipedia.org/wiki/Magnesium_oxide magnesium oxide aka magnesia] very low but nonzero water solubility
* MgO<sub>2</sub> [http://en.wikipedia.org/wiki/Magnesium_peroxide magnesium peroxide] irritant, environmentally persistent
* CaS [http://en.wikipedia.org/wiki/Calcium_sulfide calcium sulfite] decomposes with water to calcium hydroxide and hydrogen sulfide gas - [http://en.wikipedia.org/wiki/Oldhamite oldhamite] end member
* MgB<sub>2</sub> magnesium diboride (high temperature superconductor)
* CaB<sub>2</sub> calcium diboride ??

most water stable solid fluorides from abundant metals
* TiF<sub>3</sub> titanium fluoride
* MgF<sub>2</sub> magnesium fluoride aka sellaide
* CaF<sub>2</sub> calcium fluoride aka fluorite

== dangerous compounds to stay away from ==

* solid nitrogen (except you want to make highly potent explosives)
* AlP extremely toxic
* Al<sub>2</sub>S<sub>3</sub> toxic - H<sub>2</sub>S generation
* sulphur phosphorus compounds - highly toxic
* Fe<sub>3</sub>P highly toxic
* BF<sub>3</sub> BCl<sub>3</sub> PCl<sub>3</sub> all highly toxic (but gasseous anyway)

== reactive but useful compounds ==

Many other highly reactive compounds may be useful when encapsulated and serving a non structural like electronic or other function.

* Mg<sub>3</sub>N<sub>2</sub> [http://en.wikipedia.org/wiki/Magnesium_nitride magnesium nitride]

= III - V compounds =

Note that nitrogen and phosphor forms four covalent bonds here instead the usual three.
This can be pictured as their lone pair of electrons sticking into the electron deficient orbitals of boron or aluminum.
The character of this bond is distributed over all four bonds such that perfectly tetrahedral symmetry is reached.

* BN cubic boron nitride - highly stable and similar to diamond
* BP boron phosphide - rather stable thus maybe low toxicity (?)
* AlN aluminium nitride - slowly attacked by water - low toxicity
* AlP aluminium phosphide - '''highly toxic''' - releases phosphine when in contact with water

The elements Ga,In,Th & As,Sb,Bi that are also in group III and V respectively are rather scarce and thus not considered here.

Table of III - V compounds: ([http://en.wikipedia.org/wiki/Template:III-V_compounds wikipedia])

= Silicon dioxide and related compounds =

All compounds reached by full substitution of silicon or oxygen by their groupmembers carbon or sulfur respectively are rather unstable.
Partial substitutions should work though. See: [[pseudo phase diagrams]].

* allotropes SiO<sub>2</sub> (e.g. quartz,...)
* structurally equivalent solid CO<sub>2</sub> - probably explosive (similar to room-temperature solid nitrogen) since normally the well known low energy gas
* structurally equivalent solid CS<sub>2</sub> - normally a molecular liquid
* structurally equivalent SiS<sub>2</sub> - normally a soft solid made from polymeric chains

= Some interesting oddballs (not necessarily diamondoid) =

* CS2, SO3, Osmium oxide, ...

== Related ==

* For binary chemical compounds suitable for advanced APT sorted by the chemical element they contain check out the page: [[Chemical element]]