Gemstone-like compound

Diamondoid materials encompass all materials that:

• do not diffuse at room temperature
• are stiff enough to keep their shape under thermal movement
• have dense three dimensional networks of covalent bonds - (short bond loops => no polymeres)
• (not necessarily but desirable) do not react or dissolve in water

The main reason why diamondoid materials are the material of choice for diamondoid molecular elements DMEs (the constituents of artificial advanced AP systems) is that they do not jitter and wobble or even diffuse away while they are built robotically (a blind process) and that products out of those systems can be made so that they only have one to a few tightly controlled degrees of freedome. This way one can test one action at a time which enables engineering with fast progress. A systems design that poses the necessity for scientific entangling of convoluted relationships is usually considered bad. Natural nanosystems are like this because of random incremental evolution in small steps without lookahead. In this regard one obviously shouldn't copy from nature.

Wikipedia has its own page about diamondoid materials. See here: [1]

Carbons versatility

By the time of writing (2014) and the time of last review (2015) carbon is the only building material for which extensive studies about tooltip chemistry have been undertaken.
Note that just by structuring carbon (and adding a bit hydrogen as passivation agent) many material properties will be archivable. This is because diamondoid materials go far beyond the known allotropes and thermodynamically stable phases. They extend into the set of low level and high level metamaterials.

Low level metamarterials include very stable patterns that are highly ordered. Those patterns may include vacancies and may have periods of repitition of arbitrary length. Their structural alterations are small enough to influence properties that originate at such low size levels e.g. chemical electrical magnetical and other properties (especially relevant for the non mechanical technology path). A simple example of a low level metamaterial is when donation atoms are embedded in a checkerboard or other exactly periodic pattern. The set of sufficiently metastable low level metamaterials is significantly bigger than the set of designed materials that can today (2014) be cooked together by macroscopic means. This set of designed materials favours random mixing because they require very restrictive good thermodynamic accessibility.

The distinction between low level metamaterials and high level metamaterials may be difficult in some cases. Conventially doped semiconductors for example are not called metamaterials.

Beyond carbon from acetylene and methane many further studies are needed most importantly:

• machanosynthetic splitting of water for scavenging usable oxygen
• direct splitting of oxygen
• splitting of nitrogen - artificial and different to current natural or industrial methods of nitrogen fixation.
• splitting of carbon dioxide
• fluorine and the nonmetal elements of the third period

Carbon nanotubes can replace the scarce element copper for electrical cables.

Diamondoid compounds

Please keep in mind that all compounds we know of today are only those few we can create by mixing and cooking various elements or preproduced compounds together. With mechanosynthesis many more will be accessible. Although they're not in a thermodynamic minimum they'll be very stable at room temperature. A recent example is the theoretical prediction of the stability of graphitic pentagonal carbon sheets with the so called cairo pattern. The "few" compounds we can create by mixing and cooking them together are all the minerals that are documented today. These will be surveyed here. Many more meta-stable compounds will become mechanosynthesizable though for most applications the allotropes of carbon alone will suffice.

Lists of potential structural compounds

• Diamondoid biominerals ... compounds that are synthesizable under solution are of interest for technology level II to bridge the gap between technology level I and III.

• Binary diamondoic compounds

• Diamondoid compounds that contain (partially abundant) s-block metals

Metamaterials made from the basic diamondoid materials are able to emulate a lot of physical properties. Further binary ternary or higher diamondoid materials can complicate engineering design due to

• low symmetry in their crystal structure
• complex or polar surface structure which may be difficult to passivate
• lack of tensile strength
• ...

thus they may predominantly find use for special applications like as:

• slowly water dissolvable materials for better biodegradability
• laser gain materials
• infill materials
• materials with special electrical magetical or other exotic non high level emulatable properties

pure elements

• carbon sp3 network allotropes: diamond, diamonds known properties, lonsdaleite; sp2 allotropes: fullerenes, graphitic networks
• B ~four allotropes of elementar boron
• Si silicon (also cubic or hexagonal)

drawn from the atmosphere

Oxygen and nitrogen rich compounds like SiO₂ and Si₃N₄ are interesting because more than half of this material can be drawn directly from the atmosphere. When atmospheric carbon dioxide is used carbon allotropes and β-C₃N₄ can be drawn 100% from the air.

back to the atmosphere

When burning diamondoid materials (hopefully in a smart way - thus only in traces - see recycling) it strongly depends on the type of chosen material whether they convert to gasses or just reform to a glassy slag. In the latter case it will be more difficult to recover the elements in pure form. The rough rule is: When heated under oxygen mainly carbon based materials burn up almost completely while silicon or metal oxide based materials just melt to a slag. Everything in between could be possible. Certain combinations of elements can become dangerous when burned together as we know from the PVC dioxine problem.

ternary and higher compounds

Look out for rock forming minarals here.
Alkali and earth alkali compounds tend to be rather soluble in binary compounds in ternary and higher compounds they tend to form less water soluble minerals.

• Ca(OH)₂ calcium hydroxide aka slaked lime (rather water soluble)
• CaCO₃ calcium carbonate (very slightly soluble)
• MgCO₃ magnesium carbonate aka magnesite (slightly soluble)
• Mg₃B₇O₁₃Cl boracite (very slightly water soluble)
• ... many more

In the earths mantle and crust silicon and oxygen are the most abundant elements. On the borther to earths outer core this changes to iron and nickle. Down there the most abundant minearls are made from mixture of those elements: olivine/peridot Of interest as diamondoid materials may be the pure end members of the mixing series:

• Fayalite Fe₂SiO₄
• Forsterite Mg₂SiO₄
• Tephroite Mn₂SiO₄ (less interesting since Mn is more scarce)
• Titanium Silicate TiSiO₄
• Titanite or Sphene CaTiSiO₅ (optical dispersion exceeding diamond; birefringent)

In nature when iron rich metal is available in stochiometric excess heterogenous pallasite is formed. This rock looks really beautiful and can be found in some meteroids.

Another interesting tertiary material would be CSiO ₄
a solid intermediate material between CO₂(gas) SiO₂(solid quartz): [2]

compounds which contain relatively scarce elements

Those may be useful in the lower technology levels or special tooltip chemistry where only very small amounts are needed (e.g. germaium containing tips).

• molybdenium oxide structures
• germanium compounds
• ... many more

Sources for elements

Carbon is planned to be drawn from [ethyne] more commonly known as the welding gas acetylene. It has the advantage of a triple bond that when partly split up provides four unpassivated bonds and it's carrying around a minimal amount of hydrogen. Since DMEs are compact and crystal like they have a lot less surface than the source molecules and thus require a lot less hydrogen passivation. Ethyne cant be delivered in highly compressed gasseous form since it explosively decomposes. It is hardly soluble in water but well soluble in acetone ethanol or dimethylformamide. Ethyne can be manufactured by the partial combustion of methane and thus potentially be gained from renewable resources.

If one looks at the most common or most easily accessible elements and their simplest compounds one finds a list of potential structural building materials:
Link to a graphic of the most common elements in the earths crust from Wikimedia Commons.

Most easily accessible are nitrogen oxygen and argon since they can direcly be drawn from the atmosphere.
To investigate:

• Means for filtering/capturing N₂ and O₂ each selectively from the atmosphere.
• Mechanosynthetic tooltips and manipulations to gain reactive moieties out captured N₂ and O₂.

Chlorine could be drawn from common salt leaving behind sodium. To get this residual into a nonreactive environmentally acceptable form that could be used as structural material rather than just constituting waste one could chose from sodium minerals. To prefer are compounds with no crystal water and simple formulas with only elements of high importance for APM (that is which we are likely to gain control of soon after reaching technology level III) like e.g. jadeite and further ones to find.

The 13th group

Elements of the 13th group (the boron group) are special in that they can form electron deficiency bonds.

If elements of this group come into play (are used in DMEs) the view of atoms as construction blocks with a fixed number of connection points breaks down. E.g. when boron comes in contact with nitrogen the lone pair of nitrogen plucks into the electron deficient hull of boron making the two atoms more behave like two four valenced carbon atoms (with a little polar/ionic character). Prime example: ammonia borane. This is not yet handeled correctly by the software Nanoengineer-1 so it is advised to refrain from using 13th group elements for DME design for now.

In high quanities both solvated aluminum and boron compounds are alien to human and natural biology. Intake can lead to bad or unknown effects. Thus one might refrain from using strongly water soluble compounds of 13th group elements. Some information can be found here: boron and water (de); aluminum and water (de)

In tooltip chemistry boron and aluminum may be useful as tool-tips for the handling of atoms with almost full electron shells like oxygen fluorine sulfur and chlorine effectively increasing their normally low bond number. (To verify!)

Todo

• add some beautiful images of minerals in their gem grade form
• pseuso phase diagrams