A critical comparison of equilibrium, non-equilibrium and boundary-driven molecular dynamics techniques for studying transport in microporous materials
G. Arya et al., A critical comparison of equilibrium, non-equilibrium and boundary-driven molecular dynamics techniques for studying transport in microporous materials, J CHEM PHYS, 115(17), 2001, pp. 8112-8124
Transport in an idealized model with variable pore diameter as well as an A
lPO4-5 zeolite is examined using three different molecular dynamics techniq
ues: (1) equilibrium molecular dynamics (EMD); (2) external field nonequili
brium molecular dynamics (EF-NEMD); and (3) dual control volume grand canon
ical molecular dynamics (DCV-GCMD). The EMD and EF-NEMD methods yield ident
ical transport coefficients for all the systems studied. The transport coef
ficients calculated using the DCV-GCMD method, however, tend to be lower th
an those obtained from the EMD and EF-NEMD methods unless a large ratio of
stochastic to dynamic moves is used for each control volume, and a streamin
g velocity is added to all inserted molecules. Through development and appl
ication of a combined reaction-diffusion-convection model, this discrepancy
is shown to be due to spurious mass and momentum transfers caused by the c
ontrol volume equilibration procedure. This shortcoming can be remedied wit
h a proper choice of streaming velocity in conjunction with a well-maintain
ed external field, but the associated overhead makes it much less efficient
than either the EMD or EF-NEMD techniques. (C) 2001 American Institute of
Physics.