Hj. Kreuzer et Sh. Payne, Stretching a macromolecule in an atomic force microscope: Statistical mechanical analysis - art. no. 021906, PHYS REV E, 6302(2), 2001, pp. 1906
We formulate the proper statistical mechanics to describe the stretching of
a macromolecule under a force provided by the cantilever of an atomic forc
e microscope. In the limit of a soft cantilever the generalized ensemble of
the coupled molecule/cantilever system reduces to the Gibbs ensemble for a
n isolated molecule subject to a constant force in which the extension is f
luctuating. For a stiff cantilever we obtain the Helmholtz ensemble for an
isolated molecule held at a fixed extension with the force fluctuating. Num
erical examples are given for poly (ethylene glycol) chains.