ThermoChemistry Analyzer

[sattars]

Dear ATK Users,
I want to use ThermoChemistry Analyzer to study the following reversible reaction: 2L means Bilayer, <----> stands for reversible reaction

2L MoSe2 (solid) + Te (gas) <----> 2L MoTe2 (solid) + Se (gas)

I build 2L MoSe2/MoTe2 (solid) and used "Calculate CrystalThermoChemistry" template and added the output to database.
I want to ask few things:
1> When adding them to thermochemistry database, how to use the option of multiplier? 2L MoSe2 have 6 atoms, is it 1/2 that will be used or 1/1?
2> I do not understand how to take Se/Te as gas molecule? I took only one Se or Te atom in a box and treat it as a solid but it didn't work, and perhaps phonon calculation give some error.
3> Assuming the reversible reaction is occurring at 673 K and 110 mTorr , how can I adjust the pressure and temperature in the reactants and products of solids or gas? Is it the same pressure used for both reactant and products?
Your input will be highly appreciated.
Thanks,

[sattars]

Anyone have suggestions on this?

[Tue Gunst]

There are two use cases of the multiplier:
1) To balance the chemical reaction. There should be a balance in the chemical reaction to secure that the number of each element is the same in the reaction.
Notice that you can click the yellow "auto balance" warning in the products overview to let the GUI balance the reaction.
2) To compare similar reactions with different numbers of equivalent/similar reactants or products.
For the purpose of consistently comparing several reactions, it is necessary to put the reaction enthalpy on an equal footing. Therefore it might be necessary to scale reactions to be comparable (on the same energy scale).
Trivial example: doing the same simulations with twice the number of the same reactants and products one needs to scale by a factor of 2 to get the same result.

For the gas analysis: there are dedicated workflows in the workflow builder to make sure that you perform the calculations correctly for either surfaces or gas elements.
There are different classes (CrystalThermoChemistry and GasThermoChemistry) for to be used for either crystals or liquids.

For the pressure and temperature: In the analyzer, you can modify the partial pressure for each element separately (it is a simple click on each product/reactant). Everythink in the analyzer is visualized as a function of the temperature.

A tutorial in using the analyzer can be found here:
https://docs.quantumatk.com/tutorials/thermochemistry_analyzer/thermochemistry_analyzer.html

Hope that clarified your questions,
Tue