Application to Solid Form Selection

These two linear relationships between and and G appear to be quite simple (BSSE-free) and useful approximations, which enable the evaluation of the H-bonding energy in solid state using theoretical [66] or experimental (derived from X-ray or synchrotron diffraction experiment [67, 68]) energy densities. In the latter case the electronic kinetic energy density distribution, G, is derived from the following accurate approximation for closed-shell interactions (like H-bond is) in terms of experimental electron density, p, and its Laplacian V p at the BCP (in a.u.) [69]  

Using Equation 3.7 and the local form of the virial theorem [62] (in a.u.), 

However, while QTAM-based approaches (3.5) and (3.6) allow H-bonding strength ranking in molecular crystals, they require actual H-bonding geometry information to perform the predictions. Therefore, the drawback of these desalptor-based methods is that they cannot be directly used for the assessment of the likelihood of an unknown missed stable form. 

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