# Tag Info

15

There are a few recent atomic partial charge schemes that are useful. You mentioned the electrostatic fitting schemes. These seek to best match the electrostatic potential of the molecule / system, but wouldn't be ideal for your situation. They have problems fitting charges on "buried atoms" such as the metal center of your complex, because they have little ...

10

I have looked for a similar set of benchmarks and haven't found one, unfortunately. Hopefully the data referred to in the comments comes through! In the meantime, I have an MIT-licensed implementation of the Wolf-like alternative to Ewald that @PhilHasnip linked to. Here is the repository. Forces and stresses are available. You could try benchmarking against ...

10

The Jmol software is able to plot different surfaces. In the example below, the system is a Mobius strip and the ESP was calculated using MOPAC but as Jmol is full compatible with Gaussian outputs, I think there will be no problem. Mobius strip structure: Mobius solvent-accessible surface (SAS): Mobius electrostatic potential mapped on solvent-accessible ...

6

The open-source program Multiwfn (http://sobereva.com/multiwfn/) contains a module that calculates the electrostatic potentials. According to Tian Lu, it has been quite thoroughly optimized for speed. Depending on your workflow, you may even be able to obtain the electrostatic potentials by calling Multiwfn in a black-box manner through command line, without ...

5

It would help to know what you need the potentials for, since this will affect the techniques that are necessary to evaluate the potential. Point charges are trivial, as the potential generated by each charge is just -Z/r; the trick is mostly how to make the evaluation efficient, this is achieved with methods like fast multipoles or particle mesh Ewald. (...

5

If you know the Gaussian basis set and the density matrix, the task simplifies to the calculation of nuclear attraction integrals. The electron density is expanded in the basis set as $$n({\bf r}) = \sum_{\mu \nu} P_{\mu \nu} \chi_\mu({\bf r}) \chi_\nu({\bf r}).$$ When you substitute this into your equation, you get  V({\bf r}) = \sum_{A=1}^{N_{\rm atoms}}...

3

In short, the polarization catastrophe is the fact that the classical description of polarization applied to point dipoles contains a singularity which occurs at a distance which should regularly be sampled in the course of ordinary classical dynamics. More specifically, the polarization catastrophe is the failure that happens when one tries to describe the ...

3

A straightforward way to model the interaction of charged species with a surface is to use a cluster model instead of simulating the surface as a slab with periodic boundary conditions (1). Cluster models are not perfect, they can be affected by border effects that require large clusters, to be representative of the bulk system, by coverage effects, as a ...

2

I already did the same type of calculation but for different system (functionalized carbon nanotube interacting with heavy metals). About your workflow, the only step I will do different is that instead a single point optimization I'll run a full geometry optimization. This is due that you can not be sure that the point you selected from the scan correspond, ...

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