Free-energy calculations - Theoretical Biophysics Group

Reaction coordinate–based free-energy calculations A vector field approach
Derivative of the free energy with respect to the order
parameter:
dA(ξ)
dξ
= − 1
β
1
Q(ξ)
dQ(ξ)
dξ
Partition function:
Q(ξ) = δ[ξ − ξ(x)] exp[−βU(x)] dx
The δ–function can be viewed as a square pulse of
width ∆ξ. Q(ξ) is an integral over a thin slab of
configurational space, i.e. a sum of the Boltzmann
weight over the volume elements vi(ξ), so that:
Q(ξ) = 1
∆ξ
exp[−βUi(ξ)] vi(ξ)
i
Chris Chipot Free-energy calculations