278781 On-the-Fly Free-Energy Parameterization Using Temperature-Accelerated MD
We discuss a method for parametric calculation of free energy functions in arbitrary collective variables using molecular simulations. The method, termed “on-the-fly paramterization (OTFP)” fits the framework of the heterogeneous multiscale method and uses a variant of temperature accelerated molecular dynamics (TAMD ) to evolve the parameters of any free energy function to optimum values by minimization of a cumulative gradient error. We first illustrate how the method performs using simple examples that prove the underlying assumptions of TAMD, most importantly that it accurately reports free-energy gradients while exploring collective variable space. As practical examples, we show how OTFP can be used to derive coarse-grained pairwise effective potentials for systematic coarse-graining. In particular we compare effective potentials derived for coarse-grained water with those derived using force-matching  and minimization of relative entropy . OTFP may be slightly advantageous because the acceleration afforded by TAMD can provide statistics more efficiently than the thermal ensemble-averaging approaches used by the other methods.
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