"Including the Dispersion Attraction into Structure-Adapted Fast Multipole Expansions for MD Simulations" Konstantin Lorenzen, Christoph Wichmann and Paul Tavan
J. Chem. Theory. Comput. 10, 3244-3259 (2014).
Molecular dynamics (MD) simulations of protein-solvent systems, which are modeled by polarizable or non-polarizable all-atom force fields and are enclosed by periodic boundaries, require accurate and efficient algorithms for the computation of the long-range interactions. A possible choice is the fast structure-adapted multipole method called SAMMp/RF (Lorenzen et al., J. Chem. Theory Comput. 2012}, 8, 3628-3636). It is based on p'th order Cartesian Taylor expansions of the electrostatic interactions, on an adaptive and hierarchical decomposition of a macromolecular simulation system into a quaternary tree of nested atom clusters, and a reaction field (RF)correction originating from a distant dielectric continuum. Here we substantially extend this method by adding q'th order Taylor expansions of the dispersion attraction and by formulating an interaction acceptance criterion for cluster-cluster interactions, which is based on substance-specific accuracy estimates. As a result we obtain with the default expansion orders (p,q) = (4,1)a family of MD algorithms SAMMχ4,1, which comprises carefully balanced compromises χ between accuracy and efficiency ranging from ``accurate'' (χ = a) to ``fast'' (χ = f). Issues of accuracy and efficiency are discussed by sample simulations of liquid water and methanol using simple non-polarizable and complex polarizable model potentials. Here it is shown that the computational effort scales linearly with the number N of atoms. For a complex polarizable water model these simulations also show that SAMMχ4,1 is by factors between two (χ = a) and five (χ = f) faster than its predecessor SAMM4. Other benefits, which arise in simulations employing polarizable force fields with a high degree of local complexity, are also discussed.
BMO authors (in alphabetic order):
Polarizable force fields for molecular mechanics from first principles
Long-range electrostatics in molecular dynamics simulations
QM/MM hybrid descriptions of solutes in complex solvents