A Modified Shake Algorithm for Maintaining Rigid Bonds in Molecular Dynamics Simulations of Large Molecules
We present a new modification of the SHAKE algorithm, MSHAKE, that maintains fixed distances in molecular dynamics simulations of polyatomic molecules. The MSHAKE algorithm, which is applied by modifying the leapfrog algorithm to include forces of constraint, computes an initial estimate of constraint forces, then iteratively corrects the constraint forces required to maintain the fixed distances. Thus MSHAKE should always converge more rapidly than SHAKE. Further, the explicit determination of the constraint forces at each timestep makes MSHAKE convenient for use in molecular dynamics simulations where bond stress is a significant dynamical quantity.