Solvation Entropy in Jaguar

Jaguar implements the solvation entropy method from Garza [323]The total entropy of systems in solution can be expressed as:

S = S_vibrational + S_{translational} + S_rotational + S_cavity

There are three variations of the solvation entropy that can be computed, which differ in their approximation of the cavity entropy. S_ω calculates the cavity entropy using the Pitzer acentric factor of the solvent, ω. S_ε and S_εα both use the scaled particle theory to calculate the cavity entropy, and depend on the dielectric constant ε (S_ε and S_εα) and the thermal expansion coefficient α (S_εα only).

You can calculate solvation entropy by specifying the solvation_entropy and solvent keywords in the gen section of the Jaguar input file, which are set to off (0) and water by default. If solvation_entropy is set to a value besides 0, all three approximations are calculated, skipping any that do not have the necessary solvent parameters supplied. For each approximation calculated, two Maestro properties are generated. The necessary parameters and generated Maestro properties for each approximation are listed in the table below.

A solvation entropy calculation changes the Entropy and Total Free Energy of a system (compared to using the ideal gas entropy) to those of the solvation entropy version selected by the solvation_entropy keyword value. If a selected approximation cannot be calculated due to missing solvent parameters, the Entropy and Total Free Energy are updated in the following priority order: S_ε, S_εα, S_ω. For example, if you set solvation_entropy = 1, but the Pitzer acentric factor ω is not available for the solvent, the Entropy and Total Free Energy Maestro properties use the values from S_ε instead.

To calculate solvation entropy with a custom solvent, set the keyword solvent=other in the gen section of the Jaguar input file. You must then supply the following parameters:

• garza_solvent_mol_weight
• garza_solvent_density
• garza_solvent_volume
• garza_solvent_surface_area
• garza_solvent_rad_of_gyration

You must also supply at least one of these properties:

• garza_solvent_acentric_factor
• garza_solvent_dielectric
• garza_solvent_expansion_coeff