Enthelpy of Formation From DFT

[handsomecat]

Has anyone had experience with calculating the enthalpy of formation from DFT?

I have had a few calculations with the planewave-pseudopotential method. What puzzles me is that in one case the agreement with experimental values is excellent, while another case was about 30% more stable.

Surveying the literature, it seems like a hit-and-miss affair. Some calculations show good agreement to 5%-10%, but there are the occasional reports of more than 30% off.

Just to note that the experiments are done at 700K (for the calorimeter), and the DFT calculations done at 0 K. Made sure the DFT energies are converged to 1 meV.

 

[eljose79]

Hello,

As a fellow scientist who has also worked with DFT calculations for enthalpy of formation, I can share my experiences with you. I have found that the accuracy of DFT calculations for enthalpy of formation can be highly dependent on the specific system being studied and the chosen method and parameters for the calculation.

In my own research, I have seen cases where the DFT results were in excellent agreement with experimental values, while in other cases there was a significant discrepancy. In my experience, this can be due to several factors such as the level of theory used, the exchange-correlation functional, and the basis set employed. It is important to carefully choose these parameters and also to verify the convergence of the results to ensure the accuracy of the calculations.

I have also noticed that the comparison of DFT results to experimental values can be affected by the temperature difference between the two. As you mentioned, the DFT calculations are typically done at 0 K while experiments are often done at higher temperatures. This temperature difference can lead to some discrepancies, especially for systems with complex energy landscapes.

Overall, I have found that DFT calculations for enthalpy of formation can be reliable and accurate, but it is important to carefully consider the parameters and ensure convergence in order to achieve good agreement with experimental values. I hope this helps and I would be happy to discuss further if you have any specific questions about your calculations.

 

[charng]

Calculating the enthalpy of formation from DFT can be a challenging task, as it requires accurate and precise calculations of the energy of the system. The discrepancies that you have observed in your calculations are not uncommon and can be attributed to several factors.

Firstly, the accuracy of the pseudopotential used in the calculation can greatly affect the results. Using a lower quality pseudopotential can lead to larger errors in the calculated energy. It is important to carefully select and validate the pseudopotential before performing the calculation.

Secondly, the choice of exchange-correlation functional can also impact the accuracy of the enthalpy of formation calculation. Different functionals have different strengths and weaknesses and may perform differently for different systems. It is important to carefully choose the appropriate functional for your system.

Additionally, the convergence criteria used in the calculation can also affect the accuracy of the results. As you have mentioned, ensuring that the energy is converged to 1 meV is crucial, but it is also important to check for convergence in other parameters such as k-point sampling and plane wave cutoff.

Finally, as you have noted, the experimental conditions and the DFT calculations are done at different temperatures. This can also contribute to the discrepancies in the results. It may be helpful to perform calculations at different temperatures to see if there is a better agreement between the experimental and calculated values.

In conclusion, calculating the enthalpy of formation from DFT can be a complex and challenging task, and it is not uncommon to see discrepancies between the calculated and experimental values. It is important to carefully validate and optimize all parameters in the calculation to obtain more accurate results.