PRL Abstract
Abstract
Extended system path integral molecular dynamics algorithms have
been developed that can generate efficiently averages in the
quantum mechanical canonical ensemble
(Tuckerman,Berne,Klein,Martyna J. Chem. Phys. 99 2796, 1993).
Here, the corresponding
extended system path integral molecular dynamics algorithms
appropriate to the quantum mechanical
isothermal-isobaric ensemble with both isotropic and full
cell fluctuations are constructed. This is accomplished by
deriving appropriate dynamical equations of motions
and developing reversible multiple time step algorithms to
integrate these equations numerically. The new methods
are tested on model, a particle in a periodic potential,
and realistic, liquid and solid para-hydrogen and liquid
butane, systems.
In addition, the methodology is extended to treat
path integral centroid dynamics scheme,
(Cao and Voth, J. Chem. Phys. 99, 10070, 1993), a novel method
which is capable of
generating good semiclassical approximations to quantum mechanical
time correlation functions.