Rational Design of Nonbonded Point Charge Models for Highly Charged Metal Cations with Lennard-Jones 12‑6 Potential

Here,
we developed nonbonded point charge models using a simple
Lennard-Jones (LJ) 12-6 potential for highly charged metal cations
(18 trivalent and 6 tetravalent ions) for use with 11 water models
of TIP3P, OPC3, SPC/E, SPC/Eb, TIP3P-FB, a99SB-disp, TIP4P-Ew, OPC, TIP4P/2005, TIP4P-D, and TIP4P-FB.
The designed models simultaneously reproduce the hydration free energy
(HFE) and ion–oxygen distance (IOD) in the first hydration
shell with an error within 1 kcal/mol and 0.01 Å on average,
respectively, and yield reasonable coordination numbers for most cations.
Such performance is equivalent to the previously reported point charge
models using a more complex 12-6-4 LJ-type potential, while the LJ R parameters of our models are much close to Shannon’s
revised effective ion radii than that of the 12-6-4 models. Our designed
models overestimate the diffusion constants of several trivalent ions
by 5–68%. The performance in predicting osmotic coefficients
of trivalent chlorides in aqueous solution depends on the salt type.
A calibration of cation–anion interacting LJ parameters reproduces
the experimental osmotic coefficients of an AlCl3 solution
at 0.2–3.0 mol/L. The effectiveness of our new models is further
demonstrated by simulating a metalloprotein system with four force
field/water combinations. This work facilitates accurate modeling
of metal-containing systems by a variety of force fields and water
models in aqueous solution.