Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C₁− C₁₀

Intermolecular interactions in molecular crystals: what’s in a name?

“…The CE-B3LYP estimated lattice energies are À69 (HCB) and À115 (HBB) kJ mol À1 , compared with sublimation enthalpies of 88 AE 12 kJ mol À1 (from 12 measurements) for HCB, and a single value of 118 kJ mol À1 for HBB. 54 (We note that the interaction energies reported in ref. 52 for HCB are all $25% greater than the present CE-B3LYP results, but we cannot identify the origin of this difference).…”

CrystalExplorermodel energies and energy frameworks: extension to metal coordination compounds, organic salts, solvates and open-shell systems

“…The electrostatic terms are essentially identical, as expected, but the PIXEL dispersion and repulsion components are all greater than those from the CE-B3LYP model, by factors of approximately 1.3 and 1.5, respectively; polarization terms are too small for a useful comparison. Total energies are more similar, with PIXEL values larger than CE-B3LYP by $15%, and this difference is reflected in the lattice energies obtained by summation of pairwise energies to convergence: À71 (PIXEL) versus À63 kJ mol À1 (CE-B3LYP), both comparing favourably with the median value of À69.4 kJ mol À1 from a large number of experimental sublimation enthalpies (Acree & Chickos, 2016). We note that the PIXEL result is based on optimization of parameters to fit experimental sublimation enthalpies, whereas the CE-B3LYP result is based on a fit to DFT energies.…”

“…Both calibration approaches have limitations of course. Experimental sublimation enthalpies are known for several thousand organic and organometallic molecular crystals (Acree & Chickos, 2016, with estimated uncertainties typically $5 kJ mol À1 for organics and $24 kJ mol À1 for organometallics (Chickos, 2003). Experimental sublimation enthalpies are temperature dependent and smaller in magnitude than the corresponding lattice energy by approximately 2RT (Gavezzotti & Filippini, 1997;Maschio et al, 2011;Otero-de-la-Roza & Johnson, 2012).…”

Weak interactions in crystals: old concepts, new developments

“…The sublimation enthalpy, or sum total of intermolecular interactions in a crystal, is a further two orders of magnitude lower, 43-47 kJ mol À1 from different measurements. Finally, the energy differences between polymorphs are usually in single units of kJ mol À1 , comparable both to the thermal noise at room temperature (kT = 2.5 kJ mol À1 ) and to the error with which the sublimation enthalpy can be measured (ca 5 kJ mol À1 for organic and 24 kJ mol À1 for organometallic compounds, see Acree & Chickos, 2016, and beyond the reliability limits (ca 10 kJ mol À1 ) of the most sophisticated DFT calculations (Mackenzie et al, 2017). This ranking illustrates sharply the intrinsic difficulties of analysing intermolecular forces.…”