# Tag Info

11

It's possible to estimate solution-phase dielectric constant from a molecular dynamics simulation using this formula: $$\epsilon_{r} = 1 + \frac{4\pi}{3Vk_{B}T}(\langle \mathbf{P}^{2} \rangle - \langle \mathbf{P} \rangle^{2})$$ Where $V$ is the volume, $k_{B}$ is Boltzmann's constant, $T$ is temperature, and $P$ is the dipole moment defined as: \$\mathbf{P} ...

8

There are several protocols. Since you mention that you're mostly looking for trends, I'll give the faster method, e.g. by Jason Gilmore: "Expanding and Testing a Computational Method for Predicting the Ground State Reduction Potentials of Organic Molecules on the Basis of Empirical Correlation to Experiment" J. Org. Chem. 2012, 77, 15, 6423–6430 ...

5

Gaussian itself doesn't have any way of computing sigma-profiles on its own. As you noticed, it has the scrf=COSMORS keyword, but this just produces a file that is used by a dedicated program (e.g. COSMO-RS, COSMOtherm). On the Gaussian side, it really is as straightforward as using that keyword. Here is a minimal example: #p B88-VWN-P86/TZVP scrf=cosmors ...

4

Just throwing a couple of ideas out there: (i) Perform a free energy perturbation or potential of mean force calculation as available in typical classical MD setups. For known salt systems in water, this is well studied and should result in decent results (e.g., Joung and Chaetham's paper). (ii) Do a classical MD in explicit solvent for the solute of ...

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