Abstract

Recently, a new approximate method called ‘Quasicentroid Molecular Dynamics (QCMD)’ was developed for the dynamical simulation of condensed-phase systems such as liquid water and ice. The success of QCMD in being an accurate approximation to Matsubara dynamics, called for the extension of the method to other rigid molecular systems such as ammonia and methane. In this talk, we explore prospective methods that generalize QCMD which can potentially be used to simulate such systems. One such method adopts the same theoretical framework as QCMD , but defines quasicentroids in terms of relative bond-angle coordinates and is thus named ‘Bond-Angle Quasicentroid Molecular Dynamics’ (BAQCMD). Preliminary numerical results on condensed-phase water and ammonia show that BAQCMD exhibits artificial frequency shifts in the bend mode spectra, whose origin is similar to that in Centroid Molecular Dynamics (CMD), while getting the stretch mode spectrum right. Another approach towards generalization of QCMD uses the bonds and bond angles in the molecules instead of relative bond-angles to define quasicentroids, in contrast to the BAQCMD approach. Currently, efforts are underway to check the accuracy of this method in approximating Matsubara dynamics.