In this note, we propose a mapping from the spatial coordinates of an atomi
stic polymer chain to its 'primitive path' (PP), a concept being frequently
used in the framework of reptation models. For the model to be presented,
the projection preserves as much structure of the atomistic chain as approp
riate to replace an atomistic chain on a prescribed (parameterized) coarse-
grained level. We present an efficient numerical method to extract a PP as
well as an analytic approach to study the conformational properties of the
coarse-grained chain in an approximate fashion. The knowledge of the PP is
a prerequisite to facilitate tests of mesoscopic descriptions of polymeric
fluids, in particular in the framework of nonequilibrium thermodynamics, an
d allows for a thorough analysis of atomistic chain configurations on a 're
levant' coarse-grained level. (C) 2001 Elsevier Science Ltd. All rights res
erved.