TRUES — Calculate the true solvation free energy.




The keyword TRUES tells AMPAC to calculate the true solvation free energy, which is the final heat of formation plus solvation free energy for the geometry in solution minus the final heat of formation for the gas-phase geometry. (Notice the use of the widespread convention by which heat of formation is used to denote the sum of the electronic energy and nuclear repulsion with a particular choice for the zero of energy and without including vibrational energy.) The TRUES keyword must be used in conjunction with the HGAS=n.nn keyword, where n.n is the gas-phase heat of formation. It is strongly recommended that the gas-phase heat of formation be obtained with a geometry obtained using the same method in the gas-phase and the liquid-phase optimization. This provides no problem when a rigid solvation model is used (e.g., SM5.2R or SM5CR), in which case any reasonable gas-phase geometry may be used in solution, though the models were parameterized using HF/MIDI! geometries. However, when liquid-phase geometry optimization is performed, using SM5.2/X or SM5C/X, for example, HGAS=n.nn should specify a gas-phase heat of formation calculated with method X and using a geometry optimized in the gas-phase with method X.




SM5.2, SM5.2R, SM5C, or SM5CR and HGAS.

Default value:


See also: