Molecular volume difference method radius

The dimensions of the sides of the parallelepiped are conveniently taken as the difference between extreme atomic points along the inertial axes plus the largest atomic radius. An analytical calculation of molecular volume is also possible [12], although differences between the various methods of calculation usually do not exceed a few percent for non-strained molecules. 

FL, and the difference in dipole moments determined from the plot is 2.36 D if the Onsager radius is 0.33 nm [53]. The Onsager cavity radius was obtained from molecular models where the molar volumes were calculated by CAChe WS 5.0 computer program. The simplest method to estimate the cavity radius is to assume a = (3y/47r) 3, where V is the volume of the solute. 

The volume of space bounded by the solvent-accessible molecular surface is called the solvent-excluded volume because it is the volume of space from which solvent is excluded by the presence of the molecule when the solvent molecule is also modelled as a hard sphere. Moreover, the interstitial volume is the volume consisting of packing defects between the atoms that are too small to admit a probe sphere of a given radius in practice, it is calculated as the difference between the solvent-excluded volume and the van der Waals volume. An analytical method was developed by Connolly able to calculate the solvent-excluded volume [Connolly, 1983b] several other numerical and analytical approaches have been proposed. 

Here, the concept of particle scaling introduced in SPT is combined with equation (30) to evaluate Gc. This kind of relationship has been validated by a molecular dynamic study made by Postma et al. who performed a computer simulation to create five cavities of different sizes in water using simple point charge water molecules (see Free Energy Changes in Solution and Monte Carlo Simulations for Liquids for a review of computer simulation techniques). The numerical results from molecular dynamics simulation correlate very well with the cavity volume (computed from cavity thermal radius. Figure 3). A comparison between the isothermal compressibility method and SPT is given in Section 3. 

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