My current research involves finding the properties of U(VI) sorption on Biotite, and my current team has been using only the final enthalpy to evaluate whether a reaction occurred. I am currently trying to devise a new method to do that, which includes finding the enthalpy of formation of each of the compounds involved in the reaction. These values are then used to calculate the energy that would be consumed/released in the desired product considering a pre-determined equation, and cross checked with the enthalpy of formation of the geometry optimization of said product to see whether the reaction actually happened. I hope this makes sense.
The CASTEP output however has been a little confusing. What I have been doing is using the calculated all-electron energy of each atom involved in the compound and subtracting the with the final energy of the geometric optimization to find the enthalpy of formation of said compound. I have been doing the same thing with the pseudo-potential values, and the results for the same compound are off by a factor of 10^3. I am not sure which value to use, and I’m also not 100% sure if the method makes physical sense.
The equation I've been using to calculate the formation enthalpy is:
ΔH_f = (E_f - Σ(n*E_i))/n_total
Where:
ΔH_f is the formation enthalpy
E_f is the final enthalpy from the geo-opt output
n is the number of atoms of a certain element
n_total is the total number of atoms in the compound
E_i is the individual ground-state energy of each element (either the AE or pseudopotential output)
Thank you so much!
Vladimir Turovtsev Please help me. i need experimental values for ∆fH◦ (0K) H◦ (298K) − H◦ (0K) S ◦ (298K) for transition metals to calculate enthalpy of formation
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