Infrastructure for bespoke LJ parameter assignment based on QM calculations | Sophie Kantonen | Concept is to reduce number of adjustable parameters by not having LJ types but instead to parameterize a mapping from QM to sigma & epsilon for each atom in the molecule. (https://bit.ly/2VnnIsE). See also D Coles’s methods. JW – Maybe could look at implementing this in the toolkit. Touch base with engineering team later in May. DLM – Performance of this method? SK – MEasured using HVap, seems comparable to GAFF, with far fewer parameters. CB – I like the idea. As you put more charge on an atom, the radius goes up, the density goes up. So we’d expect a correlation between charge and radius or beta. MKG – One thing I’d hope to change is that, for a given element, beta determines sigma and epsilon. So sigma and epsilon are correlated. We could introduce another degree of freedom to uncorrelate these. … (I lost track of the discussion here) CB – This is reminiscent of Simon’s property calculation work, which implicitly considers all sorts of intermolecular interactions CB – It’d be interesting to see whether, emerging from the map potential, which is based on electronic structure, a correspondence for the purely empirical LJ that come out of the purely-empirical fit. This way, map potentials could guide parameter types. MKG – The challenge is that, when you have a lot of LJ types, it’s hard to be confident that they’ve been optimized enough. This is my big motivation for using less overall parameters CB – If, out of the mapping, bins appear, then this is a good guide to separating parameter types.
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