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SMIRNOFF: Allow vdW potentials other than 12-6 Lennard-Jones #46
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A crucial detail to consider: non-bonded interactions on virtual sites are hard-coded to only support Lennard-Jones parameters, even if zero. (If a Buckingham potential is used in the |
Are there cases when virtual sites have any repulsion/dispersion parameters? Generally, they would only have charges, since the goal is to create a more accurate electric field - although I can imagine a case where one would want to add some sort of repulsion to prevent accidental instability, though the functional form there is somewhat arbitrary. |
IIUC the current interest is only in moving around the location of charges and the early prototypes have focused on that. (Or least in atomistic simulations, not looking at CG/UA/hybrid approaches.) I can't say much more about the scientific possibilities but, since the spec includes vdW parameters on virtual sites, we've put a lot of work into ensuring the machinery is there in the infrastructure. |
The current SMIRNOFF specification states:
and promises:
Users are already doing this, so it would be useful to hash out the details of proper support of this behavior so as to avoid large deviations in the future. (Must expressions be algebraic, or will there be a set of English strings that encode specific functional forms?)
Aside: it's confusing that a default value is specified but explicitly not supported. It's also not consistently what the reference implementation does:
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