Free-energy calculations - Theoretical Biophysics Group

36 POHORILLE ET AL. (2010)
37 LU ET AL. (2003, 2004)
38 LEE, SCOTT (1980)
Free-energy perturbation calculations Improving the efficiency of FEP calculations
Performing a forward calculation from state i, corresponding
to λi, to an additional intermediate at λi+∆λ/2,
and a backward calculation from state i + 1 — which corresponds
to λi + ∆λ — to the same additional intermediate.
The difference in the free energies obtained from these
calculations is equal to ∆Ai,i+1. Combining forward and
backward FEP equations, 36
∆Ai,i+1 = − 1
β ln 〈exp −β∆Ui,i+1/2 〉i
〈exp β∆Ui,i+1/2 〉i+1
Simple overlap sampling (SOS) method 37 — one of the
oldest techniques for improving FEP calculations. 38 In
general, markedly more accurate than simple averaging.
Chris Chipot Free-energy calculations