Thermodynamic potentials

Question: Which is the correct thermodynamic potential to look at that needs to be minimized
in the chase for in vacuum force applying mechanosynthesis in machine phase systems?

Normal natural chemistry

For normal chemical reactions in a solvent or gas
what needs to go down for the recreation to proceed in a forward direction
is the Gibbs free enthalpy or the Helmholtz free energy of the entire system. That is for chemical reactions that happen:

• under constant temperature (for both)
• under constant pressure (for Gibbs)
• under consonant volume (for Helmholtz)

Force applying mechanochemistry

Mechanosynthesis performed in machine phase and in a practically perfect vacuum though is far form normal chemistry though.

Let's check what happens with temperature volume and pressure here.

Temperature

In force applying mechanosynthesis reaction induced temperatures changes should (and can) be avoided in the first place. Every reaction induced increase in temperature directly

• corresponds to an undesired inefficiency in energy recuperation.
• corresponds to an atom snapping to the target position and dissipating its snap vibrations to heat

this should be to a large degree avoidable by following a certain strategy.

Thermal connection mechanisms to a heat bath are

• phonons (and electrons) in diamondoid structures to the frame and the frame
• radiation heat

Given

• the relatively slow operation speeds of mechanosynthesis mills in the MHz range
• the high heat conductivity of gemstones like diamond and moissanite

there should be plenty of time for heat equilibration and this should behave rather isotherm (to check).

This is all overlays to an cooling system which's

• main purpose is to set a temperature far below room temperature for lower placement error rates and which
• has to deal with eventual dissipation heat removal even if passive cooling (or no cooling) would suffice

Endothermic mechanosynthesis

Note that reaction induced change in temperature may work more or less in reverse too.
Performing some mechanosynthesis reactions in such a way that they become endothermic.
That a reaction uses up thermal vibration energy on the tool-tip deposition contact spot to deposit the moiety at a higher energy state.
Effectively cooling down the synthesis location.

This should work especially for target structures that are less stiff than the synthesizing nanomachinery structures.
Where the target structures carries more degrees of freedom for thermal vibrations to fill up.
Where the deposition (or abstraction) synthesis step gives an expansion of phase space giving an increase in entropy.

Also as a very important point:
Force applying mechanosynthesis stiffly links the synthesis location to the drive system that may be

• a chemomechanical converter (performing chemical synthesis too) or
• a electromechanical converter.
  

If the link between the drive system and the synthesis system(s) is stiff enough then the thermodynamic potential of the system as a whole is what needs to be minimized.

This interlinkedness in mechanosyntehsizing systems may allow

• to concentrate dissipation heat in the drive system and
• to deplete dissipation heat in the the mechanosynthesis system.

This has the advantage that

• the drive system can be designed to be much less critical (or uncritical) to synthesis misplacement errors
• dissipation heat in the drive system does not dump dissipation heat in the special low temperature zone of the mechanosynthesis system where it would take extra effort to "lift" it out again.

Pressure

• enormous pressures variations are involved
• pressures are not 3D volumetric but rather directed compressions, torsions, and bends
• pressures are not only positive but very often negative too like tensile stresses

Volume

Volumes seem kind of hard to define since there are no liquids or gasses involved.
First molecule fragments are on the tool-tips then they get integrated into a solid.
Assuming temperatures are kept rather constant there should be not much of thermal expansion. So constant volume.

Filtering and "condensing" of resource molecules into machine phase

... TODO

External links

Wikipedia:

• Gibbs_free_energy
• Helmholtz_free_energy