title: Ring polymer dynamics for rigid tops with an improved integrator.
abstract: When working in curved spaces, such as those created with the introduction of holonomic constraints, or those generated from the parameters of Lie groups, the presence of a non-uniform metric significantly alters the Ring Polymer Molecular Dynamics from its Cartesian space counterpart. The presence of a nonuniform metric causes difficulties manifested in significant long-time energy drift for the common integrators, which should be absent in a good algorithm. Using a new integrator developed with the aid of the variational principle, we implement a version of Ring Polymer Molecular Dynamics adapted to curved spaces [S. Wolf and E. Curotto, J. Chem. Phys. 137, 014109 (2012)], specifically testing a symmetric ellipsoid of inertia mapped by stereographic projection coordinates. We find that the algorithm conserves the energy without long-term energy drift and converges quadratically in the time step. To test this implementation of Ring Polymer Molecular Dynamics, we compute the position-position autocorrelation function for a rigid ammonia molecule in an external field, for several values of the Trotter number.
authors.affiliation: Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA.
authors.forename: S
authors.initials: S
authors.lastname: Wolf
authors.affiliation: Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA.
authors.forename: E
authors.initials: E
authors.lastname: Curotto