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==Sublimation predictions==
The [[enthalpy]] of sublimation has commonly been predicted using the [[equipartition theorem]]. If the [[lattice energy]] is assumed to be approximately half the packing energy,{{clarify|date=June 2020 |reason=Define packing energy and explain why it is different from lattice energy}} then the following thermodynamic corrections can be applied to predict the enthalpy of sublimation. Assuming a 1 [[molar concentration|molar]] [[ideal gas]] gives a correction for the thermodynamic environment (pressure and volume) in which pV = RT, hence a correction of 1RT. Additional corrections for the [[molecular vibration|vibrations]], [[rigid rotor|rotations]] and translation then need to be applied. From the [[equipartition theorem]] gaseous rotation and translation contribute 1.5RT each to the final state, therefore a +3RT correction. Crystalline vibrations and rotations contribute 3RT each to the initial state, hence −6RT. Summing the RT corrections; −6RT + 3RT + RT = −2RT.<ref name=Gavezzotti>{{cite book |last=Gavezzotti |first=A. |date=1997 |title=Theoretical Aspects and Computer Modeling of the Molecular Solid State |publisher=Wiley and Sons |___location=Chichester}}</ref> This leads to the following approximate sublimation enthalpy. A similar approximation can be found for the [[entropy]] term if rigid bodies are assumed.<ref>{{cite journal |last1=McDonagh |first1=J. L. |author2=Nath |last3=De Ferrari |first3=Luna |last4=Van Mourik |first4=Tanja |last5=Mitchell |first5=John B. O. |year=2014 |title=Uniting Cheminformatics and Chemical Theory To Predict the Intrinsic Aqueous Solubility of Crystalline Druglike Molecules |journal=Journal of Chemical Information and Modeling |doi=10.1021/ci4005805 |pmid=24564264 |pmc=3965570 |volume=54 |issue=3 |pages=844–56}}</ref><ref>{{cite journal|last1=McDonagh|first1=James|last2=Palmer|first2=David S.|last3=Van Mourik|first3=Tanja|last4=Mitchell|first4=John B. O.|title=Are The Sublimation Thermodynamics of organic molecules predictable?|journal=Journal of Chemical Information and Modeling|volume=56|issue=11|pages=2162–2179|date=17 October 2016|doi=10.1021/acs.jcim.6b00033|pmid=27749062|issn=1549-9596|hdl=10023/11874|url=https://strathprints.strath.ac.uk/58416/1/McDonagh_etal_JCIM_2016_Are_the_sublimation_thermodynamics_of_organic.pdf|hdl-access=free}}</ref>
<math> \Delta H_{\text{sublimation}} = -U_{\text{lattice energy}} - 2RT</math>
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