A novel parametrization scheme for classical and quantum mechanical simulations of large, floppy molecular systems

We present an algorithm aimed at efficiently representing analytical full dimensional ab initio potential energy surfaces for floppy molecular systems. By introducing a new set of coordinates, we can define large amplitude displacements in one or more dimensions. Then, we use a general representation of the full dimensional potential energy surface based on a Taylor-like series expansion. Classical and quantum mechanical Path Integral Monte Carlo simulations on proton transfer in malonaldehyde and strong hydrogen bond in picolinic acid N-oxide establish the accuracy of our analytical representation and of our interpolating schemes.