Hello, I don't have experience in this feature of ORCA, I always calculate enthalpy of formation of solids using CP2K, which is easiest for this purpose. I think setting up a proper cluster and calculate this quantity using ORCA should be evidently more cumbersome and challenging.

Good day, dear Tian Lu!
I have recently become interested in computational chemistry and am trying to learn the Orca program (version 6.0.1). One of the latest tasks I have set is to learn how to determine the standard enthalpy of formation of substances, in particular, inorganic salts. Is it possible, for example, using MOL-CRYSTAL-QMMM (IONIC-CRYSTAL-QMMM does not calculate frequencies) to calculate the standard enthalpy of formation of a solid substance (example, sodium orthophosphate). I suspect that a program like CP2K would be suitable for periodic systems, but I wondered if Orca is capable of performing such calculations. And if so, what level of theory and basis would be most adequate? (I most often use PBE/def2-SVP for optimization and def2-QZVP for frequency calculations). If there are any recommendations on the choice of literature and additional software, please advise. Thank you in advance for your answer! Best regards, Vitaly B.